Ati HD4xxx + Panasonic px80 = no picture?

Hey,

I have this really odd and frustrating problem. I have a bought a HD4890 after my 8800GTS got fried, and I want to use my Panasonic px80 37" TV as my extended screen for watching movies and stuff. However I can't get this to work with DVI->HDMI. The CCC does find my TV and recognizes it as a Panasonic, but doesn't help to enable and extend it. I have tried numerous ways:

1. Tried only the TV connected = no POST/BIOS.
2. Tried all the different HDMI ports on the TV and both DVI-outputs.
3. Reinstalled drivers, tried old drivers, modified drivers.
4. Tried all the different settings in CCC (I have of course enabled the second monitor and extended).
5. Tried different cables and different DVI->HDMI adapters.
6. Tried to connect my computer with a Sony 32" LCD V4500, it works...
7. Tried connecting a laptop with Nvidia graphics to my TV, it works...
8. Tried connecting a laptop with Ati HD4650 (can't remember the exact model but a HD4xxx) to my TV, it DOESN'T work...

Here is my system info:
Asus P5N-E SLi
Intel Core 2 Duo E6600
Club3D Ati Radeon HD4890
2x1GB pc6400 Corsair RAM
Silverstone 750W PSU

All ways jolly and well with my Nvidia 8800GTS, and I cannot return my Ati because the date of return has exceed and there isn't technically anything "wrong" with the card.

Is there anybody having the same problem? Why is this combo so useless, who should I contact to get a solution...