Don't know if this helps at all but.. when I initially booted one of my MDs which was plugged into a widescreen LCD monitor via DVI cable it went through everything until it got to running the AV wizard. The screen then went black (and turned itself off as it was getting no signal) I plugged another monitor into the VGA port and there was the AV wizard running. I switched it to DVI (which is the first screen) and it changed back to the other monitor and was fine from then on.
I guess the same could be happening to you, where the TV-OUT is the same as the DVI - So my suggestion would be to try what you proposed and plug in a monitor (via VGA) for the first step of the wizard.
HTH
Darren