Please HELP!!! ipod restores but stuck on apple

I've had the same issue across three iPods: I sync the device with my library, and shortly after beginning use it freezes up, resets, and gets stuck on the Apple logo. Yesterday, one Apple employee was able to make it function properly for a good few hours, but now it's back on the Apple logo. This guy also confirmed the hard drive was perfectly fine. The simple solution of putting the iPod into disk mode and then restoring on iTunes doesn't seem to work. What is going on? I'm fed up at his point and seriously considering switching to a different mp3 player. A year of dealing with this problem on and off is far too long.