I recently picked up a new mobo and a pair of Corsair CX600's so I could pull the cards out of my file server, where they were baking the crap out of my drives. I've got the new system running with one 6870 on the first CX600, but I'm having some odd behavior with the second, which will be powering a pair of 5830s.
When I jumper the PSU (green PWR_ON to black ground) and turn everything on, it spins up and all seems well, but after about 30 seconds or so the PSU just shuts off.
My initial thought was that it required some 3.3V or 5V load in order to stay up, however this is where it gets weird - if I jumper the PSU and power it up with nothing connected, it stays on indefinitely without any problem..
I've got several other Corsair PSUs - HX650, HX750s and CX430s, and all of them work just fine jumpered. Architecturally, this CX600 should be near identical to the CX430, so I'm a little stumped why it'd behave differently. I haven't yet tried swapping it with the working CX600, will be doing so in the morning, I'm just wondering if anyone has seen this kind of behavior with a jumpered PSU before?
 These are the CX600 V2's, 80+ and 480W rated on the 12V rail.