Not sure if you still have this problem. I had the same problem and I reset the TV and that solved it. For doing a reset to default settings, just turn on the TV while pressing the exit button on the remote.
Just had an issue after 5 months of working without issue. Issue being this past week all 4 HDMI ports stopped working with my LED tv, the PS3 (connected to any hdmi port) works, HD/DVR--nothing. I have used 3 different HDMI cables, component cables, and 2 tv's hooked to this HD/DVR. I just returned (the other day) the HD/DVR for another unit, still nothing from Comcast, but PS3 works on all outputs. Comcast tech just left a few minutes ago and says something is up with my HDMI as both my Samsung LED 6000 series and a lower end 27 inch HDTV are not working ( realy ???? ). It just sounds odd to me that for 5 months I have had ZERO issues and now they (Comcast) are saying my HDMI ports are frying their HD/DVR's .. I am at a loss for their reasoning but can anyone explain to me how this could even remotely be ?