Oh man, I thought it was just my crappy old router causing the problems! I've just been too lazy to call them to replace it. I'm going to tweet at them right now. Edit: Reading the tweet thread, classic interaction: ATT says "please click this to check your connection", guy replies back and says "I think we know more about networks that you do, please get a network admin in here".
I'm in the same boat. If the dozens of IT pros who are complaining about this can't get AT&T to swap out a single router card, what hope do most folks have?