Do you have the same problem when you cancel OC ?
I'm not sure it's reason but, I had a similar usb problem (lockdown) while trying my first OC settings with my current board.
There is an extra "2-port USB / Gameport module" which came with the board. If your problem occured with them, try not to use that ports.
I don't think any other reason for now.
yours respectfully... Stonegolem