I had somewhat of a similar problem recently. I had turned off my computer and when I turned it on a couple of days later, the monitors wouldn't come on and I wouldn't get the passed-POST-beep. Tried several times, no change. Tried two different graphics cards, no change. One time I tried, I had managed to unplug the cable going to a 7-port powered hub and it passed the POST. Turned off the machine and installed the original graphics card again and the machine would start up when the hub was unplugged. Plugged the hub back in and the machine comtinued to boot up and I didn't have any problems after that (I didn't shut down the machine until I had to leave for work so I don't know how it will bwhave when I get back). This was a 7-port powered hub from DX.

Stig