a coworker of mine just purchased one of these and i am having similiar issues configuring it for pc monitor use. everything is practically identical.
i will say that on my display at home (different hdtv) i have it set to "monitor scaling", this doesn't seem to be an option with the win98 or fx series of cards. my 6800gt and/or windows xp does have this option however. this may be a result of his current nvidia driver... or the fact he's still using windows 98.
at any rate, on this sanyo lcd hdtv most resolutions display fine up to and including 1280x720 but scaling is off, leaving a good many lines off all four sides of the display.
the first change i'm going to make is an upgrade to windows xp, then upgrade the nvidia drivers if needed. i'll report back with results but in the interim any feedback is appreciated.