When using Limewire on an XP -PC, I was told:
"Task Manager has been disabled by your administrator"
It turned out to be malware in the registry.
Limewire may be innocent even if I think it is involved since I never have encouterered this before and I got it shortly after I started to use it.

Has this happened to you?

If this is done deliberately, I dislike Limewire even if it is done to improve uesful downoads from my machine? Don't you agree?

There are ways to solve this:
http://216.239.59.104/search?q=cache...disabled&hl=no

Another way is to do a roll back.