Well I ordered a cheap £30 motherboard from ebay (Intel DQ45CB) with the latest Q45 chipset for the LGA 775 platform. It's worth a shot
"Sounds like that chip just isn't supported."
The chip has been running fine for years... but it's just now when I upgraded the GPU that it decided to start having issues. I read that PCI-E slots are linked to the FSB which leads me to think that this upgrade has unearthed this instability from running an unsupported FSB speed... maybe the other GPU's don't cause this problem because they don't pull as much bandwidth from the controller... I'm not too sure though.