I'll say it. I can NOT fix that.
I feel much better now.
What I've got here is a failure to communicate (sounds familiar) between my XFX HD-585A-ZNFC Radeon HD 5850 video card-hdmi- my ONKYO TX-SR606 receiver-hdmi-my Element PLX4202B plasma TV.
If I do not have my video card installed picture fits perfectly on 1024x768 which I believe is TV's native resolution. When I install my video card (tried more than 10 different drivers, now with Catalyst 12.1) picture is larger than TV (a little bit from all 4 sides). ANNOYING.
Looks like driver problem or maybe it is time for new TV and receiver.