It's a strange error. It tunes fine for a couple of channels and then it craps out saying that it can't reference the ATSC tuning space after already doing it 2-3 times. I'll try to get Win7 up and running this weekend and see if I can figure out why it's doing it.
Can you run a scan in the HDHomeRun Setup and post the DigitalCable.xml that is created? I'll create a custom qam.ini that will only have the channels that you receive. I'd be interested in seeing if it works.