A lot of ppl are getting this when trying to sync movies. Simple but daft solution:

Go to 'Run' in start menu and type in c:\WINDOWS\system32\devmgmt.msc

This brings up your device manager. Keep this window open as you will need to get to it quickly.

Open itunes.

Connect your ipod and on the summary screen check the box enable disc use.

Click apply and quicky right click on any of the items in the device manager window and then 'scan for hardware'

Once this is done you should be able to go back to itunes and sync your ipod!
I've tested on an Ipod with the said issue and can confirm it works as it says on the tin

Hope this helps others