I have no answer to your question, but i can try. Let an administrator look at your computer and scan for errors.
Sounds a file being replicated from a pk3 file to temp folder, and gets corrupted when it gets in the temp folder, try to make a check disk.
( Just a guess, not sure. )
It also sounds like some sort of Policy that denys, but still have access to delete the file, but not change inside it.
( Still just a guess, and still not sure. )