iTunes Adding Lyrics Problem& How to maintain everything in library when reinstalling

Using Windows XP (not sure about mac's), when you try to add lyrics to your music, a major error happens. I'm not sure what causes it, but it happens almost everytime I tried adding lyrics:
If you put lyrics on a song on iTunes, it will not show up in the file's properties (or vise-versa). Often, the lyrics get erased in iTunes.... then when you try to rewrite the lyrics on iTunes, or try to play the mp3 on iTunes, it will not load. After deleting it from the library, and trying to re-add it, it will not work!! restarting computer doesn't help. In this case, do I have to reinstall iTunes?? It's not like the file got corrupted since it can play normally on any other players, but just not on iTunes. Won't add/play
If the only way is to reinstall iTunes, is there a way to keep my playlists with all the Ratings, and other edited Song Info intact?
Or is there a wa to fix this problem and re-add the songs to iTunes w/o uninstalling iTnes?

Help plz :'(