what I would try and do is the following. Backup your Ipod so that you have all your files in the iTunes library.
Try to restore your ipod by :
Because Restore erases all of the songs and files on iPod, make sure to back up any files you've saved on the iPod disk. All of your songs, videos, podcasts, audiobooks, and games can be loaded back to your iPod provided that you have them stored in your iTunes Library.
iPod (5th generation)
How to restore your Fifth Generation iPod (iPod with video)
1. Make sure you’ve installed the latest version of iTunes.
2. Open iTunes, and then connect your iPod to your computer.
3. After a few moments, it will appear in the Source pane in iTunes.
4. Select your iPod in the Source pane and you will see information about it appear in the Summary tab of the main iTunes window.
5. Click the Restore button. A window will appear asking "Are you sure you want to restore the iPod "iPod" to its factory settings? All of your songs and other data will be erased."
6. Click Restore again. (If you're on a Mac, you'll then need to type in your password.)
7. During stage 1 of the restore, a progress bar will appear on the computer screen indicating that the first stage of the restore process has started. When this stage is completed, iTunes will instruct you to leave iPod connected to your computer to complete restore.
8. During the stage 2 of the restore process, the iPod will show an Apple logo as well as a progress bar at the bottom of the display. It is critical that the iPod remains connected to the computer or iPod Power adapter during this stage. Note: The progress bar may be difficult to see since the backlight on the iPod display may be off.
9. After stage 2 of the restore process is complete and the iPod is connected to the computer, the iTunes Setup Assistant window will appear asking you to name your iPod and choose your syncing preferences similar to when you connected your iPod for the first time.
Step 6 is a fun one. Here you can hold down left shift, then click this should open a directory tab that allows you to use different firmware for your ipod. You can download the different *.ipsw firware files at http://www.felixbruns.de/iPod/firmware/ More instructions on the shift-restore are of course available through Google :)
After the restore you will have to re-sync your ipod to get your files back on it, Hope this helps and good luck to you