Try shutting down PCStitch completely and then double-clicking on the pattern to open it within PCStitch. However, it depends on what the pattern is. Remember that PCStitch is not the only program to use the ".pat" file extension. Older PatternMaker files use it as well. The double-click will only work if PCStitch is the default application associated with the extension.
If you can't load anything after a shutdown, try a reboot. If you still can't load anything, you may have something corrupted in the install and a re-install may be needed.
If none of this works - contact Mark. It's beyond what I can figure out.
Yep, tried all that and uninstalled and reinstalled. I don't know what happened to that file but I deleted it and am starting over on that pattern. If I don't try and open it the program worked fine. I sent the information on like the program asked before I deleted.
I hope you weren't too far along on your pattern. I have no idea why one you created from scratch would suddenly do that but you took the right action. If there is an option to report a bug - TAKE IT!