Everytime I download a song, any song, I get the message,"Limewire has detected a corruption in the file". This happens everytime. What's going on?

well some users don't check there files, and then share it without knowing it is corrupt, or some may deliberately share corrupt files.

Right mouse click on the file you want to d/l and do a bitzi lookup. This will tell you information on the file if there is any available.