Soldato
It's a 42" Panasonic - it displays the bios fine when booting from my GTX660. I'm going to update the motherboard bios tonight as I realised it's on an old version.
I have a Panasonic 42" plasma screen as well and i can say i had a problem where when i booted the machine and went into the bios i could only see half the screen, i havent read all through this post but the but i have i presume your symptoms are similar?
This happened with -
Amd 5850
Amd 7970
Amd 5800k with Radeon HD 7660D gpu
I read somewhere its to do with the 1:1 ratio not being a true input or something with the panasonic.
Hope this helps, my current vtx 290 flashe to 290x isnt connected to my tv so cant say if it would be the same but i would bet my house it would be.