New iPad not charging via USB? Check here
In scouring the net for news on the Apple iPad (since, you know, I was unable to get Saturday delivery on mine) I ran into quite a few complaints of people saying that their USB ports would not charge the iPad.
Keep in mind, all USB is not created equal. Some USB ports only provide 500mA of power, the iPad needs a full 1000mA of power to charge.
Check the specs on your USB ports before getting to worked up on why your iPad won't charge, it will likely end up being a power problem on that USB port only.
Hope this helps.
(Source: Consumer Reports Electronics Blog: Charging the iPad: Hit or miss)