I'm quite out of my depth here, but the sort of thing I think might be likely is a changed registry entry. Since there are 10's of 1000's of these beasties, it's a good place for programs with hooks ie malware to hide some of their nasties, it sounds like it could be something leftover after uninstalling a program that has altered or deleted a specific registry entry. Very weird. Pprune is the only affected function on your computer? I would look at a Hijack-This scan. Maybe post the logfile on a computer geek forum if it's too confusing (and they tend to be, a bit.) Good Luck.