Dear cullumbd,
If you are using copy and paste, it sounds like a data- or installation-specific bug. Clipboard operations in Windows are basically client-server data operations using a certain mime type. First, rather than allowing Windows to work out the mime type automatically just using generic copy-paste, try specifying the mime type by using "paste Special" instead. If several formats are listed, see what happens with each one.
If the file still crashes, try pasting it first into PAINT and then copy it from paint into progeCAD. If that crashes, save as a file and insert into progeCAD using the image tools.