OK, dig this: I usually plug my iPhone into my PowerMac at work to charge at some point during the day, but today, it won't charge. At first I thought it was the sync cable, but plugging in a coworker's iPod to the same USB port with the same cable results in a charging iPod.

So then I thought that it was my iPhone, that somehow it was broken. But plugging it into the Dell behind me charges it, so what's the deal? What really simple thing am I missing here?