diff --git a/src/Convert/Convert_ConicToBSplineCurve.cxx b/src/Convert/Convert_ConicToBSplineCurve.cxx
index bfc7f3fcfe..62f428d339 100644
--- a/src/Convert/Convert_ConicToBSplineCurve.cxx
+++ b/src/Convert/Convert_ConicToBSplineCurve.cxx
@@ -503,11 +503,22 @@ void Convert_ConicToBSplineCurve::BuildCosAndSin(
       alpha_2 = alpha * 0.5e0 ;
       p_param = - 1.0e0 / (alpha_2 * alpha_2) ;
      
-      if (alpha_2 <  M_PI * 0.5e0) {
-	tan_alpha_2 = Tan(alpha_2) ;
-	value1 = 3.0e0 * (tan_alpha_2 - alpha_2) ;
-        value1 = alpha_2 / value1 ;
-        p_param += value1 ;
+      if (alpha_2 <  M_PI * 0.5e0) 
+      {
+        if (alpha_2 < 1.0e-7)
+        {
+          // Fixed degenerate case, when obtain 0 / 0 uncertainty.
+          // According to Taylor aprroximation:
+          // b (gamma) = -6.0 / 15.0 + o(gamma^2)
+          p_param = -6.0 / 15.0;
+        }
+        else
+        {
+          tan_alpha_2 = Tan(alpha_2) ;
+          value1 = 3.0e0 * (tan_alpha_2 - alpha_2) ;
+          value1 = alpha_2 / value1 ;
+          p_param += value1 ;
+        }
       }
       q_param = (1.0e0 / 3.0e0)  + p_param ;
       
diff --git a/src/Draw/Draw.cxx b/src/Draw/Draw.cxx
index ed04b5f8fc..30e6a626d1 100644
--- a/src/Draw/Draw.cxx
+++ b/src/Draw/Draw.cxx
@@ -248,7 +248,7 @@ void Draw_Appli(Standard_Integer argc, char** argv,const FDraw_InitAppli Draw_In
   // *****************************************************************
   // set signals
   // *****************************************************************
-  OSD::SetSignal();
+  OSD::SetSignal(Standard_False);
 
 #ifdef _WIN32
   // in interactive mode, force Windows to report dll loading problems interactively
diff --git a/src/Draw/Draw_Window.cxx b/src/Draw/Draw_Window.cxx
index 7b9208e3e4..7378ca4b30 100644
--- a/src/Draw/Draw_Window.cxx
+++ b/src/Draw/Draw_Window.cxx
@@ -2079,7 +2079,7 @@ static DWORD WINAPI tkLoop(VOID)
 #endif //#ifdef _TK
 
   // set signal handler in the new thread
-  OSD::SetSignal();
+  OSD::SetSignal(Standard_False);
 
   // inform the others that we have started
   isTkLoopStarted = true;
diff --git a/src/QABugs/QABugs_11.cxx b/src/QABugs/QABugs_11.cxx
index a7099d5681..43766d5fe9 100644
--- a/src/QABugs/QABugs_11.cxx
+++ b/src/QABugs/QABugs_11.cxx
@@ -88,7 +88,7 @@
 #include <BRepFeat_SplitShape.hxx>
 #include <BRepAlgoAPI_Section.hxx>
 
-#if ! defined(WNT)
+#if ! defined(_WIN32)
 extern ViewerTest_DoubleMapOfInteractiveAndName& GetMapOfAIS();
 #else
 Standard_EXPORT ViewerTest_DoubleMapOfInteractiveAndName& GetMapOfAIS();
@@ -2357,7 +2357,8 @@ static Standard_Integer OCC5698 (Draw_Interpretor& di, Standard_Integer argc, co
   return 0;
 }
 
-#ifdef WNT
+// stack overflow can be successfully handled only on 32-bit Windows
+#if defined(_WIN32) && !defined(_WIN64)
 static int StackOverflow (int i = -1)
 {
   char arr[2000];
@@ -2366,8 +2367,10 @@ static int StackOverflow (int i = -1)
     StackOverflow(i-1);
   return i;
 }
+#endif
 
 // this code does not work with optimize mode on Windows
+#ifdef _WIN32
 #pragma optimize( "", off )
 #endif
 static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, const char ** argv)
@@ -2394,7 +2397,7 @@ static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, co
       di << " 4 / 0 = " << res << "  Does not Caught... KO"<< "\n";
       Succes = Standard_False;
     }
-#if defined(SOLARIS) || defined(WNT)
+#if defined(SOLARIS) || defined(_WIN32)
     catch(Standard_DivideByZero)
 #else
     catch(Standard_NumericError)
@@ -2427,16 +2430,17 @@ static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, co
       di << "\n";
       Standard_Real res, a= 4.0, b=0.0;
       res = a / b;
-      di << " 4.0 / 0.0 = " << res << "  Does not Caught... KO"<< "\n";
-      Succes = Standard_False;
+      di << " 4.0 / 0.0 = " << res << "  Does not Caught... OK"<< "\n";
     }
     catch(Standard_DivideByZero) // Solaris, Windows w/o SSE2
     {
-      di << " Ok" << "\n";
+      di << " KO" << "\n";
+      Succes = Standard_False;
     }
     catch(Standard_NumericError) // Linux, Windows with SSE2
     {
-      di << " Ok" << "\n";
+      di << " KO" << "\n";
+      Succes = Standard_False;
     }
     catch(Standard_Failure) {
       //cout << " Caught (" << Standard_Failure::Caught() << ")... KO" << endl;
@@ -2484,16 +2488,17 @@ static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, co
       
       (void)sin(1.); //this function tests FPU flags and raises signal (tested on LINUX).
 
-      di << "-- "<<res<<"="<<r<<"*"<<r<<"   Does not Caught... KO"<< "\n";
-      Succes = Standard_False;
+      di << "-- "<<res<<"="<<r<<"*"<<r<<"   Does not Caught... OK"<< "\n";
     }
     catch(Standard_Overflow) // Solaris, Windows w/o SSE2
     {
-      di << " Ok" << "\n";
+      di << " KO" << "\n";
+      Succes = Standard_False;
     }
     catch(Standard_NumericError) // Linux, Windows with SSE2
     {
-      di << " Ok" << "\n";
+      di << " KO" << "\n";
+      Succes = Standard_False;
     }
     catch(Standard_Failure) {
       //cout << " Caught (" << Standard_Failure::Caught() << ")... KO" << endl;
@@ -2520,11 +2525,13 @@ static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, co
     }
     catch(Standard_Underflow) // could be on Solaris, Windows w/o SSE2
     {
-      di << " Ok" << "\n";
+      di << " KO" << "\n";
+      Succes = Standard_False;
     }
     catch(Standard_NumericError) // could be on Linux, Windows with SSE2
     {
-      di << " Ok" << "\n";
+      di << " KO" << "\n";
+      Succes = Standard_False;
     }
     catch(Standard_Failure) {
       //cout << " Caught (" << Standard_Failure::Caught() << ")... KO" << endl;
@@ -2544,11 +2551,11 @@ static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, co
       di << "\n";
       Standard_Real res, r=-1;
       res = sqrt(r);
-      di<<" "<<res<<"=sqrt("<<r<<")  Does not Caught... KO"<<"\n";
-      Succes = Standard_False;
+      di<<" "<<res<<"=sqrt("<<r<<")  Does not Caught... OK"<<"\n";
     }
     catch(Standard_NumericError) {
-      di << " Ok"<< "\n";
+      di << " KO"<< "\n";
+      Succes = Standard_False;
     }
     catch(Standard_Failure) {
       //cout << " Caught (" << Standard_Failure::Caught() << ")... KO" << endl;
@@ -2571,7 +2578,7 @@ static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, co
       di << "  Does not Caught... KO"<<"\n";
       Succes = Standard_False;
     }
-#ifdef WNT
+#ifdef _WIN32
     catch(OSD_Exception_ACCESS_VIOLATION)
 #else
     catch(OSD_SIGSEGV)
@@ -2587,7 +2594,7 @@ static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, co
     }
   }
 
-#ifdef WNT
+#if defined(_WIN32) && !defined(_WIN64)
   {//==== Test Stack Overflow ===============================================
     try {
       OCC_CATCH_SIGNALS
@@ -2620,7 +2627,7 @@ static Standard_Integer OCC6143 (Draw_Interpretor& di, Standard_Integer argc, co
 
   return 0;
 }
-#ifdef WNT
+#ifdef _WIN32
 #pragma optimize( "", on )
 #endif
 
diff --git a/tests/de/end b/tests/de/end
index b19b2703c6..598228e4cb 100644
--- a/tests/de/end
+++ b/tests/de/end
@@ -697,11 +697,15 @@ puts ""
 clear
 smallview
 if { $mist < 1 } {
-    if { [info exists res_2] && [isdraw res_2] } {
-	donly res_2
-    }
+  if { [info exists res_2] && [isdraw res_2] } {
+    donly res_2
+    isos res_2 0
+	fit
+	isos res_2 2
+  }
+} else {
+    fit
 }
-fit
 xwd $imagedir/${test_image}.png
 if { $mist < 1 } {
    if { [catch { Close D_Second } catch_result] } {
diff --git a/tests/de/iges_2/H9 b/tests/de/iges_2/H9
index af815a83ee..cea20ad115 100755
--- a/tests/de/iges_2/H9
+++ b/tests/de/iges_2/H9
@@ -1,12 +1,9 @@
 # !!!! This file is generated automatically, do not edit manually! See end script
-puts "TODO CR23096 ALL: CHECKSHAPE : Faulty" 
 puts "TODO CR23096 ALL: NBSHAPES : Faulty" 
+puts "TODO CR23096 ALL: TOLERANCE : Faulty" 
 puts "TODO CR23096 ALL: LABELS : Faulty" 
 puts "TODO CR23096 ALL: COLORS : Faulty" 
 
-puts "TODO CR23096 Mandriva2010: STATSHAPE : Faulty " 
-puts "TODO CR23096 Mandriva2010: Error : 4 differences with reference data found :" 
-
 puts "TODO DEBUG_OCC24121 Debian60-64 Windows: Warning: ShapeAnalysis_Surface"
 
 set LinuxDiff 4
@@ -16,11 +13,11 @@ set filename coque-sup.igs
 set ref_data {
 DATA        : Faulties = 0  ( 0 )  Warnings = 0  ( 0 )  Summary  = 0  ( 0 )
 TPSTAT      : Faulties = 0  ( 3 )  Warnings = 274  ( 4465 )  Summary  = 274  ( 4468 )
-CHECKSHAPE  : Wires    = 1  ( 1 )  Faces    = 3  ( 2 )  Shells   = 0  ( 0 )   Solids   = 0 ( 0 )
-NBSHAPES    : Solid    = 0  ( 0 )  Shell    = 0  ( 0 )  Face     = 1627  ( 1627 )   Summary  = 39245  ( 39252 )
-STATSHAPE   : Solid    = 0  ( 0 )  Shell    = 0  ( 0 )  Face     = 1627  ( 1627 )   FreeWire = 22  ( 26 )   FreeEdge  = 135 ( 135 )   SharedEdge = 17932  ( 17933 )
-TOLERANCE   : MaxTol   =   0.1961320506  (    992.8187669 )  AvgTol   =  0.0003490038155  (    0.2648369601 )
-LABELS      : N0Labels = 6  ( 6 )  N1Labels = 1642  ( 9636 )  N2Labels = 0  ( 0 )   TotalLabels = 1648  ( 9642 )   NameLabels = 1648  ( 2888 )   ColorLabels = 1644  ( 9641 )   LayerLabels = 488  ( 3995 )
+CHECKSHAPE  : Wires    = 2  ( 2 )  Faces    = 3  ( 3 )  Shells   = 0  ( 0 )   Solids   = 0 ( 0 )
+NBSHAPES    : Solid    = 0  ( 0 )  Shell    = 0  ( 0 )  Face     = 1628  ( 1628 )   Summary  = 39243  ( 39275 )
+STATSHAPE   : Solid    = 0  ( 0 )  Shell    = 0  ( 0 )  Face     = 1628  ( 1628 )   FreeWire = 22  ( 26 )   FreeEdge  = 135 ( 135 )   SharedEdge = 17944  ( 17947 )
+TOLERANCE   : MaxTol   =   4.337400808e+088  (    8.082392835e+086 )  AvgTol   =  2.040579288e+085  (    5.099401401e+083 )
+LABELS      : N0Labels = 6  ( 6 )  N1Labels = 1643  ( 9638 )  N2Labels = 0  ( 0 )   TotalLabels = 1649  ( 9644 )   NameLabels = 1649  ( 2890 )   ColorLabels = 1645  ( 9643 )   LayerLabels = 489  ( 3997 )
 PROPS       : Centroid = 0  ( 0 )  Volume   = 0  ( 0 )  Area     = 0  ( 0 )
 NCOLORS     : NColors  = 4  ( 5 )
 COLORS      : Colors   = BLUE1 CYAN1 GOLD3 GREEN  ( BLUE1 CYAN1 GOLD3 GREEN YELLOW )
diff --git a/tests/de/step_4/G7 b/tests/de/step_4/G7
index 8eb1ee9da5..92da668d93 100644
--- a/tests/de/step_4/G7
+++ b/tests/de/step_4/G7
@@ -3,10 +3,6 @@ puts "TODO CR23096 ALL: CHECKSHAPE : Faulty"
 puts "TODO CR23096 ALL: NBSHAPES : Faulty" 
 puts "TODO CR23096 ALL: TOLERANCE : Faulty" 
 
-
-puts "TODO CR23096 Mandriva2010: Error : 2 differences with reference data found :" 
-puts "TODO CR23096 Debian60-64: Error : 2 differences with reference data found :" 
-
 set LinuxDiff 2
 set filename BUC61004.stp
 
@@ -14,8 +10,8 @@ set ref_data {
 DATA        : Faulties = 0  ( 0 )  Warnings = 0  ( 0 )  Summary  = 0  ( 0 )
 TPSTAT      : Faulties = 0  ( 0 )  Warnings = 5  ( 43 )  Summary  = 5  ( 43 )
 CHECKSHAPE  : Wires    = 1  ( 0 )  Faces    = 1  ( 0 )  Shells   = 0  ( 0 )   Solids   = 0 ( 0 )
-NBSHAPES    : Solid    = 1  ( 1 )  Shell    = 1  ( 1 )  Face     = 2523  ( 2523 )   Summary  = 16186  ( 16187 )
-STATSHAPE   : Solid    = 1  ( 1 )  Shell    = 1  ( 1 )  Face     = 2523  ( 2523 )   FreeWire = 0  ( 0 )   FreeEdge  = 0 ( 0 )   SharedEdge = 6807  ( 6808 )
+NBSHAPES    : Solid    = 1  ( 1 )  Shell    = 1  ( 1 )  Face     = 2523  ( 2523 )   Summary  = 16185  ( 16187 )
+STATSHAPE   : Solid    = 1  ( 1 )  Shell    = 1  ( 1 )  Face     = 2523  ( 2523 )   FreeWire = 0  ( 0 )   FreeEdge  = 0 ( 0 )   SharedEdge = 6806  ( 6808 )
 TOLERANCE   : MaxTol   =    9.829787663  (    7.812889886 )  AvgTol   =   0.01764242132  (   0.01681498017 )
 LABELS      : N0Labels = 1  ( 1 )  N1Labels = 0  ( 0 )  N2Labels = 0  ( 0 )   TotalLabels = 1  ( 1 )   NameLabels = 1  ( 1 )   ColorLabels = 0  ( 0 )   LayerLabels = 0  ( 0 )
 PROPS       : Centroid = 0  ( 0 )  Volume   = 0  ( 0 )  Area     = 0  ( 0 )