I am having the same problem over here. It occured actually when I was in the middle of a linux install... It was going fine and then the install failed and i tried too reboot but nothing came up. Now when i boot my computer up I dont get anything on the screen or a beep. My harddrives spin and the power button doesnt work at all to power it down. I have too manually power it off via the power supply toggle.

I had just put in a brand new power supply as well caus the last one burnt out...heh and right after i put in the new one this happens.

My insticnt was too yup take out all my devices one by one and see where the problem was...well i got all the way too the ram and still no screen. So it's either the cpu or the mother board..the cpu is spinning fine so i'm assuming its the mother board..

hope someone has a solution.