Thanks for your help and offers of help everyone. Kannon solved the problem for me it was a small overlap that I had missed. Must get some new glasses!

I am using Mastercam 9.1 on WinNT4 SP6 old stuff I know. I am trying to extrude a simple solid shape using curves initially taken from a dxf file. I have checked the boundary curve are all ok no breaks etc but am now getting an error message I dont understand. "Parasolid Kernal Interface Error. PK error code: 942 curve crosses edge" What does this mean and how can I solve the problem?