I have the same card as you and am currently having problems with getting the HD channels through comcast running smoothly. I have a very similar spec machine so i don't think power is the issue. In your system you don't have a H.264 codec installed - is this correct. I know that mediaportal is using my H.264 codec to display the HD channels - however in my tvserver_tv.log they are listed as mpeg2 streams.
ie
2009-01-11 00:32:23.718565 [19]: subch:1 pid:FE video type:MPEG-2
2009-01-11 00:32:23.719565 [19]: subch:1 map pid:FE video type:MPEG-2
2009-01-11 00:32:23.719565 [19]: subch:1 pid:FF type:86
2009-01-11 00:32:23.720565 [19]: subch:1 pid:100 audio lang:eng type:AC3
2009-01-11 00:32:23.720565 [19]: subch:1 map pid:100 audio lang:eng type:AC3
2009-01-11 00:32:23.721565 [19]: subch:1 stop tif
2009-01-11 00:32:23.721565 [19]: WaitForPMT: sending PMT to CAM took 0.006 seconds.
2009-01-11 00:32:23.742565 [19]: card: Tuner locked: True
2009-01-11 00:32:23.742565 [19]: **************************************************
2009-01-11 00:32:23.743565 [19]: ***** SIGNAL LEVEL: 0, SIGNAL QUALITY: 94 *****
2009-01-11 00:32:23.743565 [19]: **************************************************
My signal is split multiple ways, which might be why I am seeing signal level of 0 and might be the cause of my problems - can you confirm that with this card you see a signal level above 0? Thanks for your help.
ie
2009-01-11 00:32:23.718565 [19]: subch:1 pid:FE video type:MPEG-2
2009-01-11 00:32:23.719565 [19]: subch:1 map pid:FE video type:MPEG-2
2009-01-11 00:32:23.719565 [19]: subch:1 pid:FF type:86
2009-01-11 00:32:23.720565 [19]: subch:1 pid:100 audio lang:eng type:AC3
2009-01-11 00:32:23.720565 [19]: subch:1 map pid:100 audio lang:eng type:AC3
2009-01-11 00:32:23.721565 [19]: subch:1 stop tif
2009-01-11 00:32:23.721565 [19]: WaitForPMT: sending PMT to CAM took 0.006 seconds.
2009-01-11 00:32:23.742565 [19]: card: Tuner locked: True
2009-01-11 00:32:23.742565 [19]: **************************************************
2009-01-11 00:32:23.743565 [19]: ***** SIGNAL LEVEL: 0, SIGNAL QUALITY: 94 *****
2009-01-11 00:32:23.743565 [19]: **************************************************
My signal is split multiple ways, which might be why I am seeing signal level of 0 and might be the cause of my problems - can you confirm that with this card you see a signal level above 0? Thanks for your help.