HDMI No Signal Error

Issue:
I've tried 2 TVs (Samsung HL67A750A1 and LNT2653HX) and they both give the same 'No Signal' error. For 8 months this setup has worked without an issue with both of these TVs.

The original issue started with the ATI 4650. The PC would still display without issue, but it would randomly freeze and then a few days later the motherboard started giving a diagnostic error code that the video RAM check during POST failed and the computer would no longer boot.

I installed an ATI 4870 I had and the computer booted fine and no more lockups. I was glad I finally figured out the issue. But then the next day the LNT2653HX LCD said 'No Signal' when turned on. A reboot/reconnect cable/re-seat video card, etc wouldn't help. I connected the PC to the HL67A750A1 and received the same error.

Tests:
Both TVs will work fine with another PC and XBox 360. I installed the 4870 in the other working PC and immediately received the 'No Signal' error. I placed my 5870 back in the working PC and while it wouldn't show POST, it did display once Windows 7 booted (interestingly when I connect through my Denon Receiver, the PC will show POST on the HL67A750A1 - just not when directly connected).

The bad PC with the 4870 will boot to Windows and I can even connect to it through RealVNC and gain access to the file shares. When looking at the display properties, it only detects a VGA connection (the RealVNC I assume). I installed Powerstrip and the EDID information it is pulling from the registry is completely wrong, stating 1600x1200, a resolution neither of my TVs support. When I try to tell it to pull EDID from the display device, it gives an error that it cannot find one.

Any ideas on what is causing this? I'm hesitant to buy a new video card, as this PC has seemed to ruin 2 so far, and maybe that isn't the issue? Is it some weird EDID issue that could be fixed? Is it my MB or PSU causing a short and blowing HDMI/DVI ports on the video cards?

I ran CPU, Memory and GPU torture tests (before I started getting the No Signal error) and didn't run across any errors nor did any temps rise to critical levels (CPU under 55 and GPU under 80).

One recent change before all this occurred is I installed a bunch of Windows Updates and RealVNC. By the time the issues started occurring, a restore point before these installs was no longer available.

Since I get 'No Signal' even in POST/bootup, I'm not even able to reinstall Windows.

PC Specs:
Foxconn ELA 775
C2D E8400
4x2GB Crucial 8500, running at factory speed and voltage (1.8)
Supermicro PCIx4 8-port SAS controller
7 hard drives JBoD
580 Watt Mad Dog PSU (about 6 years old).
Windows 7 64-bit

I'm going to tell you that you may need to check your PSU, I wonder if it's putting out the proper power as this sounds likely that it is not.