Uverse Lockups And Router Reboots?

We've had UVerse for about a year now - but lately we've had weird problems:

-about every 2-4 weeks, the router will spend a night constantly locking up and rebooting itself. ATT says they don't know why, and wanted me to check the power?? When it does this, it will do it for 30 minutes to TWO HOURS.

-every couple of days, the channels will freeze. If we change channels and then back, it returns to normal for a bit. Sometimes for a while, sometimes only for a minute. We have two boxes, each one does it. Even affects DVR playback. Internet doesn't seem to be affected, so I had originally though it was the boxes. ATT has remoted in, and can't find anything out of the ordinary.