missing songs

I recently went to update my ipod on my ibook and while updating it informed that some of my songs from some albums where missing although i hadn't deleted them myself, they just went missing. Has anyone else had this problem and/or knows how to fix it??

if youre ipod is set to auto update songs, and you took these songs out of the itunes library, theyre gonna be missing.

i have set it up to auto update but i didnt touch my itunes library, didnt delete songs, didnt move songs, didnt do anything their just missing from my computer