...

[Acejam]

...

[computerparts]

The Antec Earthwatts 650 psu should have 2 6+2 pin pci-e connectors. Modify scripts so nothing runs at bootup and see if the problem persists.

[Jack of Diamonds]

The PSU can handle a 6990 even in switch mode 2 incl. your processor and other peripherals, it's the molex converter cable which can't supply that much extra wattage.

Your best shot is leaving the switch in default position and using two separate Athena cables, if your PSU has 4 molex connectors.

The cable is designed for 6pin+8 pin cards like the 6970. There is a very high likelihood it has not been even properly tested for 8+8 pin cards which are very unorthodox
(not counting custom made ones and the ARES/MARS cards, there are only two mass produced GPUs that use that amount of power from PCI-e connectors, the nvidia gtx 590 and amd radeon 6990)