My iPod Nano 3G isn't connecting to iTunes or Windows or charges?

When I connect my iPod to my computer, the pop-up 'USB Device Not Recognised: One of the devices attatched has malfunctioned and Windows XP doesn't recognise it...' and doesn't even charge. The only way for it to charge is by loading the secret menu screen (i.e. holding centre and previous button on power-up) so it can't be my USB cable and even if it was I have tried 3! This means that I can't add, remove or edit any of the songs on my iPod now. Any help please?