i was getting this failure sometimes with my amd sempron 2800 processor. i found a new processor amd athlon64 3700. i tried this 3700 but it worked a few times and i am getting no screen failure everytime now. 2800 is working very well now. by the way, my motherboard is asus k8n.
Most likely an issue with your display (have you tried others with your build?) or the motherboard itself. For clarity though, what powers your display? A dedicated graphics card or the onboard video of your K8N?