IPod 80Gig keeps stopping during sync--stops on random, working songs HELP?

I've restored it a lot, reset it, reset my computer, brought it to the apple store and all they did was restore it...I've been trying to sync 1400 songs and it keeps stopping around 900-1100. It just says it is syncing one song but it keeps on going until it says the disk cannot be read. I can't eject it, so i just hafta pull it out; it goes black, and then when it turns back on it's either empty or has less than 10 songs. I've gone back and erased the problem songs...doesn't work. I NEED HELP this is very important. THANKS.