PSU Not Compatible?

I tried installing a Silencer Mark II 750W power supply into my Gateway-4320 01e, just to use it before the next build. However, once installed, and after getting the initial Windows splash, the screen just goes dark, as if there's no video input, but the monitor does not say so, so video input is fine. However, I can boot into the various Safe Modes, just not normal Windows. Why is this?
I put the old PSU back in and the computer booted up fine. And yes, everything was plugged in correctly.
I can't ask Gateway this since my warranty was literally 1 week out, since I bought this November 2010.
And clue as to what's gone wrong?
http://reviews.cnet.com/desktops/gateway-dx4320-01e/450...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...