iTunes keeps saying damaged library

Dunno whats happened but everytime now when i connect my ipod video itunes always pop up with an error message before it opens saying something along the lines of 'itunes library is damaged, do you want to replace this file' or something like that, and everytime it will make a new .itl file in my iTunes folder.

Anyone know whats causing this or what i can do to stop it happening? any help appreciated.