Ion,
Thanks for the advice, when I tried doing what you suggested there were no raw VW files to find the program might have changed since you used it.
I did get a reply from vizfx and there's a patch for OSX available at:
http://projects.vizfx.com/stonecad/misc/
I downloaded StoneCAD6_1_Mac.zip file and replace the original application with the newer (patched) one leaving all the rest of the folders and files in place, and everything seems to be working now.
Hope this helps.
Dennis