Make sure you have the serial number.
I don't know Apple, but you should be able to uninstall. If you have the disk, do a fresh install. If you downloaded it, use the install file you first downloaded. If not, download a copy here: Download Adobe Premiere Elements 15, 14, 13, 12, 11, 10
However, something else is wrong. The difference from 14.0 to 14.1 is not a version, it is a minor fix of minor issues.
Premier Elements makes backup files every 15 minutes or so. On a PC, they are in a "Auto Save" folder. Can you open one of those?
To reset or delete the preference file, do one of the following: Press and hold Alt+Control+Shift (Mac: Option+Command+Shift) immediately after Photoshop Elements begins launching. Click Yes to delete the Adobe Photoshop Elements settings file.
Thanks for your reply, and sorry for the slow response: it took me a while to get over my frustration enough to try.
Uninstalling and reinstalling version 14.0 didn't help -- I continued to get the same error message -- and the Autosaved files wouldn't play either. I still can't find the preferences files: pressing the keystroke sequence immediately after PE begins launching doesn't seem to do anything, but thanks for the suggestion.
...Anyway, it seems like somehow the file must have become corrupt, somehow. Other old projects *will* play, I've discovered.
It seems like PE just can't sustain big, complicated project files for long. Super black mark against the program!
Thanks again for your time.