I had this problem a couple of months after I bought it. Overnight, or in the middle of the day (I'm guessing when the DVR is supposed to be receiving the TV Guide scheduling updates), the machine would lock up with a U99 error code. Following the manual, I unplugged it from the wall, waited a minute or so, then plugged it back in. This happened daily for about a week, then stopped for about 6 months or so - no error codes, everything running fine. In the past few days, it has started up again. When I see it, I dutifully unplug, wait and replug it in, and everything seems to be fine again. It unfortunately happened the afternoon before the Smallville season premiere, and I missed it. I am updated with the latest firmware, so that's not the issue. Anyone else running into this?