Hi Rodney,
When you modify images in PI it keeps the old versions in the swap area (that's how it can undo an operation quickly.) These files are included in your project so that when you reload it the history of all the images is preserved. The error you are getting appears to imply that at least one of those files has gone missing. It could be an error on your C: drive, or maybe something deleted some of those files. Did you run any sort of disk clean up utility or do you have one that runs all the time?
If you've lost all the swap files then you're probably out of luck and won't be able to do much apart from saving your individual images and the process icons. If you've only lost one or maybe a few you might be able to save most of the project apart from the images that are directly affected. I don't know any clever way to figure this out apart from checking which images you can undo back to their original state one step at a time without error.
That's all I can suggest for now. Maybe somebody else has better ideas.
Cheers,
Rick.
