New System Upgrade GPU Power Problem

Hi

I recently purchased myself a nice shiney new cpu mobo and ddr3 ram with which to upgrade my system
full specs as below. Initially installed everything fine new installation of windows on Sata 2 Disk loaded without problem. Then I began loading various patches and software updates. System Crashed a few times but just put this down to working out a few quirks. Then whilst powered on and running one of these updates the system crashed again displayed just a bright blue screen and then died.
I went through various diags with it and ultimately identified that the system will boot but not with Aux power connected to the GPU (It is connected via an adapter from a standard 4 pin connector).
With it connected I press the power button 1 MOBO led lights and then the PSU shutsdown. I then have to switch off the power via the switch for 10 sec or more to reset the PSU.
If I remove the aux power connector from the GPU and boot the system loads as normal. The GPU works and displays graphics and can even play games its just running at reduced performance due to the lack of power. This GPU and PSU ran fine in my old rig but that was just single core AMD xp3700 with 2gb Ram.
Im thinking perhaps the PSU is on its way out and is struggling with the extra demand
or is it an issue with the power connector on the GPU which is shorting out the Power supply.
What do people think?

Intel Quad Yorkfield Q9550 Processor
4Gb ACZ tech ddr3 1333mhz Ram
Gigabyte S775 Intel P45 ATX A L UltraD3 MOBO
Gigabyte Geforce 8800GT GPU
Sata 400Gb HD
650 Watt PSU