GA-7VM400M Post Problem

Question

I have a GA-7VM400M board, the original I think. Every so often when I boot the system it won't post, just sits there. I can reset it a couple of times and it will eventially boot and runs stable for weeks on end, literally. Any ideas on why it has these intermitent posting problems? Running: ATI Radeon 9600 256mb AMD Athlon 2500+ Barton 512mb PC333 RAM