I've been on the phone with Tech Support with this exact same issue. I have an HR20-700 and was on the phone with them for 30 minutes. It is a known issue with this model, I was told by a supervisor. They told me that they will have it fixed before 1 pm est. I, and many others will be really pissed if this doesn't work today. I can tune the channel but if I switch to any other channel, I get a blank screen. I only have this problem on the ST channels. Only way I could fix it is to bring up the guide, exit back to channel, bring up miniguide with the blue button, then switch to a non-ST channel, get the blank screen and reset my receiver. My non-HD receiver in another room works fine. I am gonna scream if I can't get the games in HD today on my 60". If I have to watch on my POS 20" non HD tv, I will raise hell with them. How can you not be aware of this problem? GRRRRRRRRRRRRRRRRRRRRRR
WHEW! Ok everything is working properly on my end now. Good luck.