Well, it was a long shot because it was multiple images

It happens often enough with one image and the selection tool active, clicking (and dragging a bit) on the image to activate it, leaving a 1 × 1 byte selection, practically invisible, but you can only 'paint' and so within that selection.
BTW, are you sure the message was auto
protect and not
preserve?
I can't really think of anything else except maybe corrupt caches, or a program reset.
Try File/Preferences/Reset preferences/ delete all cache files (Active caches rebuilt on start) and restart PSP.
If that doesn't work, press and hold down a shift key when you click on the shortcut to start PSP. You'll get a dialogue about resetting to factory defaults or something like that: click Yes and PSP starts.
If you have customized your workspace you might want to save before doing this.
After reset you'll need to redo things like file locations etc. if you changed anything, and reload a saved workspace.
I hope this works, or someone with X7 can duplicate and repair the problem. Good luck.