Using own rendering architecture with OpenCASCADE

I've got an existing framework that I'd like to try using the OpenCASCADE geometry library with (3D curves, surfaces etc) but I'm having trouble getting it to compile. OpenCASCADE doesn't seem to like using STL in an MSVC environment - I'm using STLPort and VC 6.0. If I define WNT I get a conflict with the old MSVC stream classes. Any ideas anyone?

Thanks,
Michael