Both of my Premiere XL4's have been spontaneously rebooting at least twice a day since February 10th, so I'm sure it's related to bad data being delivered to them by TiVo's servers, not hardware failure. Usually the reboot is followed by the blue LED lighting up, indicating an attempt to upload a podcast to the DVR may have caused the initial crash. The DVR with fewer podcast subscriptions and Season Passes crashes less often. A similar spate of reboots happened to both of my XL4's about a year ago then corrected itself, so hopefully TiVo's engineers are working on a fix. It's nice having two identical DVRs so I can rule out hardware issues when things like this happen.