Epilogue: when I contacted ATT to provision a new cable modem and found that they'd charge me $10, I told them not to do anything, and undo any changes made that night until I could decide what to do. Then a few hours later I lost my connection, and was told that there was a line issue and that a tech could come out the next day...but the computer wouldn't let that happen, so instead it was scheduled for 3 days away.
Ug.
Thinking something was up, on Sunday I called them back up. Turns out the idiot who took my earlier call had de-activated my previous MAC and activated the one I didn't want to use. Idiots. I clearly told them to reset all my settings to how they had been. At least ATT will not charge me for the down time.
Moral of the story: don't trust your ISP farther than you can throw your modem with both hands tied behind your back.
