Problem with BRepAlgoAPI_Section

Hi,

I am having problems extracting the PCurves from a BRepAlgoAPI_Section.

I have intersected two shapes (each has a b-spline surface as its underlying geometry) and when I explore the result, I can extract Edges for all the intersections and display them. I can also extract the PCurves on my first shape, but the call to PCurveOn2 results in a unhandled exception in TKBREP.DLL.

Is there anything wrong with my code listed below?

I am using the precompiled stable release 4.0 on Windows 2000, Visual C++ 6.0.

Thanks,

Neil

BRepAlgoAPI_Section mySection(myShape1, myShape2, false);

// build b-spline curves
mySection.Approximation(true);

// make sure we find the parametric curves
mySection.ComputePCurveOn1(true);
mySection.ComputePCurveOn2(true);

mySection.Build();

if (mySection.IsDone())
{
TopExp_Explorer anExp;

for ( anExp.Init(mySection.Shape(), TopAbs_EDGE); anExp.More(); anExp.Next())
{
TopoDS_Edge myEdge = TopoDS::Edge(anExp.Current());

Handle_AIS_Shape anAISShape=new AIS_Shape(myEdge);
myAISContext->SetColor(anAISShape, Quantity_NOC_GREEN1);
myAISContext->Display(anAISShape);

double rWFirst, rWLast;
Handle(Geom_Curve) aCurve = BRep_Tool::Curve (myEdge, rWFirst, rWLast);
Handle(Geom2d_Curve) myPCurveOn1 = mySection.PCurveOn1(myEdge);
Handle(Geom2d_Curve) myPCurveOn2 = mySection.PCurveOn2(myEdge); // this call results in an exception
}
}