Download iTunes 7.7.0.43 - FileHippo.com
download that version of iTunes and reinstall, then from version 2.0.0 or 2.1, restore it AGAIN to 2.1 or 2.0 or whatever you prefer. It will then work I still have that version of iTunes in that link above, just in case it only occurs with the new version, anyways that fixed mine and I sync music and cydia etc. really really great!
1. Uninstall your itunes and reboot
2. Download that link above for that version of iTunes and install it
3. if your ipod/iphone is currently messed up because of that glitch, simply restore it back to the ORIGINAL(not custom).
4. You now have it working normally, now you can jailbreak it, I only did step 3 because I wanted to make sure most of the crap I had on it was erased etc. you can just do step 3 and 4 together... good luck