I plugged my ipod into my comp and it doesnt charge/sync with itunes/update...wut

the heck??!!? and worked fine like a week ago. i just added like 20 songs and wanna update ipod...and just updated itunes from 7.4 to 8.01

again, my ipod doesnt even charge when i plug it into the comp...the comp doesnt pick it up..its stupid. and i tried pluggin it in all the usb ports. and usb ports from my laptop too,(and my laptop doesnt even have itunes) and it didnt show up/charge, etc. but it will charge when i plug it into the wall charger though. ne ideas neone???

thank u!!