You need to have both tuners turned off for the box to be able to get updates. Many other problems can occur when you leave your receiver active for too long. Don't do it.
Actually, you don't. The only time you have to both tuners off to receive updates is if you disable daily updates. As long as daily updates are enabled on the 522, regardless of whether either or both tuners are on, the receiver will power down, do the updates, and power up. If you disable daily updates, it will only update when both tuners are off.
Really? The 522 will actually just stop you from watching your show, grab a tuner to get an update, and install it? That's really poor design. At least it can be turned off.
Yes, since it occurs at 3am, most people don't see it. If you set the update for 7:05pm, at that time, it will popup a message saying "it's time to get it's updates. Is that okay ? Yes, No, Cancel" (not the exact wording, of course ). You MUST respond or it will default to "yes". You can of course tell it "No" and continue watching TV.
You can always change it to another time if you have a timer going. I like to record a program that happens to come on at 3 am so I just rolled it up to 5 am. It is really poor design since the feature can be disabled. If it didn't give you a choice, that would be a different story. And, like hall said, if you do happen to be watching something, you can just click No.
And be forewarned, if you click "No", you raise the chances of the 522 deciding that there're errors on your HD. The ONE time I wanted to keep watching TV, it told me, later that morning, that it had to wipe the drive.