HTPC Works ok with SONY LED but not with Panny LED HDMI

My HTPC works fine when HDMI connected to a Sony LED TV but when connected to a Panny LED TV it will not even boot. I have to have the HDMI cable disconnected till it boots then I can connect the HDMI cable to the TV. When it is connected to the Panny, there is no POST display but the TV detects a connection but no display. When the HTPC is connected to the Sony, all is well. Strange the Panny keeps it from booting but works fine when connected after the HTPC is up.

Thanks. I really do not see anything that would keep the PC from booting. It does its resets and posts but it does not get any further. It is like it may be waiting for a anput from a keyboard to start the boot but since I have no display, I cannot tell. It does boot just fine with the HDMI cable removed or when connected to a Sony LED TV. The Panny is brand new. The Sony is a year old. The video card is a GT430.

Thanks for the reply. Have tried a couple of cables with the same results. As far as the drivers go the computer does not get that far in the boot to load the drivers. But the drivers have been updated within the last month to the current level at that time. The main board does not have HDMI.

Update. The video card is a Radon 6450.

I am direct connected from the video card to the TV. I even tried booting the PC with the TV off. No difference. I will try pulling the cable on the TV end and see if it boots.