Reinstall your system and your iTunes library, or just get your music, videos and photos off your iPod, and save them to your computer
1.go to music in ipod when connected to computer
2.select the songs
3.drag to the itunes area for music
4.your done
Hopefully this works for all of you like it just worked for me!
Know more about how to transfer music from iPod touch to compiuter, which included the detailed tutorials of how to transfer your music from iPod to PC.
If you follow these questions you'll figure out where the problem is coming from:
-Have you tried using a different USB port on your computer (as someone else mentioned)?
-Do you have another USB cord you can use? If so, try it and see if it works then.
-Do you have any other USB peripherals (e.g. printer, iPod, phone, mouse) you can hook up to the computer? If you do, hook it up --if it works then it's not your computer causing the trouble.
Once you figure out the source of the problem, post a reply and we can go from there.