Yeah, it's been a while since mine spannered up. Think you press the menu and centre button at the same time and keep them down for like 5 seconds then it resets. Or the play and centre button, I can't remember. One or the other. But if it still isn't having it then first put the device on hold then not on hold (ie. flip the hold switch back and fore in one movement), then do the buttons held down trick. Normally does the business.
If it still won't fix itself then let it play until the battery runs out then hope that it still works. If still acts up then hopefully within a year of buying it to send back to Apple. If you phone them they send someone to collect it (and package it for you).
One time we had a Nano that did the same thing and it took 3 recalls to get it working. Well, it worked the 1st time but they kept cocking up the sodding engraving (single quotes are not good). And waiting about 4 weeks to get it back was pissing us off. After the 2nd engraving cock up we demanded our money back. They won't do that, but after I pretty much demanded blood at the very least down the phone, then the woman said what if they could sort it out in 3 days. Eh? Yep, we will pick it up, *definitely* get it right this time, and send it back to you within 3 days. Err, ok... And yes they did as they said. Apparently if you are nice (I was the first few times) you are put through to normal support, but if you kick up a fuss like a baby then they shove you onto priority support where they definitely will sort out the problem one way or another. 3 days later got the (brand new v2 model actually) Nano back perfectly fine with the correct engraving...
So shout down the phone...
Cheers
Ps. One neat thing though, was 2 out of 3 of the ones we got back were brand new models with the full packaging etc. When I gave the stuff back to the pickup bloke they insisted on only the Nano, nothing else. So basically I have 2 free boxes. No big deal, but free headphones and baggies are nothing to be sniffed at.
I am 99% probably lying in bed right now... so don't blame me for crappy typing
Current fave quote : "She was like a candle in the wind.... unreliable...."