My usb jack on my ipod touch does not seem to be working. it will work when i plug it in my dock but it will not work when i plug it into my laptop to sync with itunes. i used to be able to sync it if i moved the cable around whilst plugged into the ipod untill it reconises it but it does not reconise it at all now. which means i cannot sync with itunes just charge it up in my dock. any ideas how to fix this?