hi
i think you might have to restore you ipod touch
http://support.apple.com/kb/HT1414
BUT BEFORE YOU DO wait for someone else to confirm that
if that doesn't work try this
http://support.apple.com/kb/HT1808
You could try and get your purchased music and apps off your touch and onto your computer by
http://support.apple.com/kb/HT1848 (transferring your purchases) , (if it still detects your touch) or do it the long and manual way to getting music off your ipod, or you could get some third party software and see if you can get the music off the ipod. (if nothing works here i will compile a list of how to do this)
Alex, Good luck 😉