Built a 1800+ amd on a soltek mb with a radeon 8500 graphics card in a case with a 400v powersupply. worked fine for one day then the next day when I tired to turn it on it powers up and doesn't show any display. There are no beeps and the hard disk and cdroms seem to power up.

Sent the mb and chip back and got a new mb and the same chip (they checked and found fault on mb)

Built it again and the same thing happend, computer not working after being left off over night. It seems to perform as normal execpt no display. Nothing was touched overnight.

Any ideas why? even a bad guess?

Install just the CPU, RAM, and video card, and place the MB on a piece of cardboard. If you get a display, then the MB is shorting out to the case. Get some paper washers and place them between the standoffs, screws, and the MB.
If placing the MB on cardboard does not work, then suspect another bad MB from a possible run of defective ones. You may want to try another brand.