In the west. Had it happen to me a couple of times over the weekend (722k). However, when I went back 5 seconds, the same clip played with sound. I thought it was my TV, but I've never had this issue with other devices connected to the TV.
Possibly on a related note, some of my DVR recordings start off with no picture/sound for 10-15 seconds. I also recently connected my external drive, and it takes roughly 1 minute to transfer every 10 minutes of programming (an hour-long show takes 6 minutes... pretty slow). I'm not sure if the box is faulty, or this is expected behavior.