It runs fine for about 1 or so hours and then shuts off.
I have a friend who was using an RM850 to power a couple of BFL 60Gh units and he reported the same thing.
I had a similar problem with an older Zalman 1000W PSU that was running a pair of ASICMiner Blades and a few USB hubs - all 12v. The Zalman would cut out after 30-60 minutes. Turned out it needed some load on the 5v rail, so I hooked up a couple of fans to the 5V and it seemed to cure the issue.
In the end up I replaced the Zalman with a Corsair CX750 which runs fine with only a 12V load. Been running 24/7 for about a month now.
Thanks! I'm using it to power a KNC Jupiter. The Jupiter requires a Molex connection in addition to the PCI-e connectors. I thought I plugged in the Molex to the 5v rail. Which seems like it should draw something???
Last night I plugged a 120mm fan into the Molex chain and set it on top of the power supply and it ran fine all night.