dont trust those dummies from genius bar there very incompetent and there techs terrible at problem solving I've figured out several problems with my ipod 30gb i used it in my car forever and never left my glove box i lost my usb cable and that's when i went to them for answers there was 2 problems 1. was my center click stopped working i fixed that by taking it apart scratching it but i fixed it what happens in the got these rubber boots glued (not very smart)under the wheel there total of 5 of them over time if you leave your ipod in hot place the glue starts melting and rubber boot start to move. 2.is try and go to local store that sells car stereos that have the ipod plug built in will let you use the ipod from the cable charge it. if your ipod works then you know it not bad
cause it should charge and play the music.anyway i think it cable problem with new USB cable they sell at the stores and don't work with 5th gen ipods. best thing is to look online for new cable that says 4th gen and up try this one
http://www.walmart.com/ip/Griffin-USB-to-Dock-Connector-Cable-for-iPod-Coiled/13 995979
don't lisen to them there trained to fix problem fast if the cant fix it they recommend you to pay upgrade price $125.00 and they send your old ipod to 3 party refurbishment center and they pay apple for the old ipods $25-$50
apple there to make money not care about you just your wallet
id say about 90% of ipods ive seen can be repairable or nothing wrong with them
long story short iam sure just your cable that bad and need to be replaced
if not walmart refund you your money and you havent lost penny
so if you like to go to local car steroe shop and tell them your looking buy radio that will play and control your ipod and you're there see if it works for your ipod there plug it in and test it for you and it free most car steroes will work with older ipods
if you ipod works then run wal-mart and buy your self new cable
hope this helps