I had the same problem after updating BIOS of my GIGABYTE 8I845 mobo 3 weeks ago. I took it to Gigabyte service centre twice. They repaired my mobo for ONLY Rs. 1000

but it worked for few hours and started giving me same problem then I took it to service centre again and asked for repair without any charges, and again they repaired it. On 11 Feb. 2008 I got my machine back to work after long wait of 3 weeks

At first they changed the BIOS chip and for second time they just cleaned the channels where we put RAM. So one thing u can do at first is to clean those channels by urself