I just had the same thing. Running 622 in single mode and lost audio on 1 tuner. Rebooted and while acquiring singal the 622 rebooted itself. Then it came on and I had audio again. However not all the guide info was there. Tried to download guide info, status bar did not move, so I stopped the Guide Info download, then while watching TV shortly after the 622 rebooted itself again. Waiting to see what happens now. Sounds like more than an isolated event or two.