My iPod Classic won't sync--I keep getting error messages.

Question

I have an iPod Classic (Late 2009) that's about a year and a half old. It just started refusing to sync with iTunes. I have a PC, and when I plug the iPod in, the computer wants to scan and fix the iPod. Whether I let it or not--I've done it both ways, multiple times--when I open iTunes, iTunes says I need to restore my iPod. It restores without glitching. But when I try to re-sync my library, I get 200-400 songs in and get an error message that a specific song can't be synced because of "error [numerical error]." I've seen "Error -50" a lot, but not always. It doesn't always get stuck on the same song, artist, or album--just somewhere in the B's, something goes wrong. At the beginning, I was seeing a "duplicate file" error message, but I haven't seen it the last 5-7 times I've gone through the restore-resync process.
I've tried manually managing the content, but the same thing happens. If it doesn't get stuck on a song, it'll say "Finishing Sync" for ages--until I have to force-quit iTunes and manually eject the iPod.
I have reinstalled iTunes--not 100%, but using their "find and replace faulty parts" option. I have an iPhone, and it syncs with no problem, and I my iTunes library itself is functioning totally normally. However, iTunes freezes a lot when I'm trying to fix this problem with my iPod, including when I first plug it in. I've had to force-quit iTunes multiple times because of this.
This all started because my iPod was skipping from about 10 seconds into one song to the next in the playlist. I figured something was wonky with the last sync, so I went to restore my iPod. When I plugged it in, I noticed that there was a software update, so I did that--I can't remember if I restored, then did the update, or the other way around. But nothing has worked since then.
It must be a problem with the iPod itself that the restore just isn't erasing, but I'm not sure where that leaves me. Help?

Answer 1

This could be an indication or a damaged or dying hard drive.  I would recommend doing a disk diagnostic on the iPod's HD using the instructions given by turingtest2 in this older thread.  He also covers what the resulting numbers indicate.
https://discussions.apple.com/thread/3784647?start=0&tstart=0
B-rock