Why not ignition? That's how I have it now, yellow to battery, red to ignition. With that setup, the Visteon HDZ actually gets power on the red wire 5 seconds before the PC powers up, since the M2-ATX has a 5-second power-on delay. It's a simple matter for me to change the wiring, if you think that will make a difference.
As for iGuidance, yes I'm using it, on COM2. However, iGuidance does not automatically run when RR starts, only when I click on the navigation screen the first time. If I never click the navigation button, iGuidance doesn't run, and I still get these HD radio errors.
I didn't get to do any more experimenting yesterday, so I will have to wait until I get home from work tonight to mess with it. Thanks for your help.