The update that was sent out before Daylight Saving time has caused a lot of problems with my 921. I now have to reboot about 3 or 4 times a day. Problems include: (1) Frequently screen comes up black when turned on or goes black while watching something . (2) In early morning, reboot results in guide having "no information" except for the programs starting in the next hour. (3) Unit fails to respond to remote or does so with significant lag. (4) Unit has blank guide, shows no timers, and/or shows no dvr recordings--fortunately reboot has fixed this so far. I didn't have this last problem until after the DST update.
I am beginning to believe they are programming in these problems to convince us to upgrade to a 622. Before the DST update, I rebooted about once a day on average. I think most of these problems are a result of the DST software update, since they increased in frequency immediately after the DST update.