USB preventing post w/ OC on Gigabyte boards

[kmeson]

I have a problem where an external USB HD, when turned ON prior to boot, prevents post when I'm OC'd (Q6600 B3 @ 3.0ghz w/ FSB 333). Turning OFF the drive solves the problem. Once booted I can turn the drive ON and am 100% stable as far as I'm able to test (couple hours OCCT). The behavior is the board resets while inspecting RAM. I've run memtest 86+ through several passes tests with out error. It's not a big deal except when I forget about the solution.

I ran across this quote in the forums:

Turning off Detect Legacy USB Devices helps in combating the cold boot issue on the Gigabyte boards but its not 100% effective.

I'm not sure turning off legacy USB solves the problem, I've not tested it yet. I'm interested in theories on the cause and the experience of others with similar problems. My theory is it's power related, a hardware problem, perhaps too many devices on the bus. A powered USB hub might solve the problem.

Machines specs:
Gigabyte P35-DQ6 v1
8gig Corsair 4x2 800@5-5-5-18
Q6600 B3 @ 3ghz using 9x333mhz
Seasonic M12 700watt PSU

Thermals:
32-35c Idle
56-60c Load

USB devices:
Logitech 3100 keyboard + mouse
Logitech MX Revolution mouse
Apple Aluminum Keyboard
Dell USB hub in 2405 LCD
Dell USB hug in 2001FP LCD