So I have a Crosshair V formula -Z with a 9590. Seems I got it narrowed down to my USB 3.0 ports on the I/O. Any time I have anything plugged into one of the USB 3.0 ports I get boot hang with the Q-Code 66. Unplug device and it boots without issue. I have current drivers installed but still get issues with the ports. Any suggestions or pointers?