TopoDS_Shell.ShapeType() returns Random numbers

Hi,

I am new to OpenCascade and created a new Box by using BRepPrimAPI_MakeBox.
The box is constructed correct ( tested with STEP output ).

When accessing the ShapeType() method (Box.ShapeType()) it will give me random numbers and when accessing the second time the program crashes (Segmentation fault , is trying to access 0x00 ).

Can you give me some hints which could cause this?

Cheers Tobias