ATI Radeon 4600 HD - No signal ...

Hi ,
Sorry for my bad English.
I have an ATI Radeon 4600 HD on my PC which is running Win -7.
I installed the latest Catalyst driver from ATI.

The problem :
I connected my PC to my Plasma TV, which is 720 but capable of showing 1080p broadcast.
I can see picture when I connected the PC to TV through VGA cable.
BUT- When connecting through HDMI, I cannot see any picture, even not the boot process when powering on the PC... no signal !

I'm clueless and really almost gave up...
Does anyone have a clue for that ?

Thanks !!

I think that HDMI is the problem then . . . . The connection of the card to that port might be damaged !!!!