I have a problem in a lot of my logs where, after attempting to decrypt them, I get the following error message:

"An error occured while attempting to decrypt your file. Please reboot or try again on another computer."

I haven't formatted the computer, uninstalled Messenger or Plus!, or otherwise made any changes to anything involving the logs... It isn't even all the logs; but at least a few from nearly every month won't open. I obviously haven't tried them all, but I've found some from a couple of months ago that won't open, and some from last year. Some of them used to open and only recently stopped working.
Are they corrupted? Is there any way to open them at all? I've tried nearly everything. =/

Hmm... No one has any idea, then?

Did you try on another computer?

If you can on another computer, try the procedures on  Sunshine's post: Encrypting, decrypting etc. of Plus! chatlogs

Maybe with those methods, you can decrypt and re-encrypt them.

I can help only this much. Last thing I can recommend: A clean install