Hard locks - Radeon x1650 Pro

Couldn't find anything in search to fix my problem, I made a thread like this about 6-months ago and the problem did go away by just simply updating my BIOS. But It's returned.

Specs:
AMD Athlon 64 4000+ 2.4Ghz
1.5GB of RAM
ATI Radeon x1650 pro (PCIE)
ASUS A8N-E
550W PSU


I keep getting hard locks while playing ANY game or 3D application and a rare hard lock while just browsing the web. When I get a hard lock the screen freezes for a bit and the sound just goes into a endless annoying loop and get a "signal not found" message by my monitor so I have to manually reset the computer.

I've tried just about everything and I've came to the conclusion that It is my video card maybe It's overheating or bad ATI drivers. I've uninstalled and updated my video card drivers, chipset drivers, BIOS, and windows. I've tested each stick of ram stick individually and each ram slot through Memtest. I've ran tests on my hard drive using tools from the manufacturers site. I've cleaned my whole computer from dust and residue, here's a SS from Sensors View Pro ( http://img259.imageshack.us/img259/8749/tempspr8.png ). Thermal grease on the video card is dry if that means I have to apply some new grease and that's causing the problem.

I'm completely lost here, I'm getting a new video card soon but I want to figure out If It's the card or my computer. Thanks in advance.