So I turned off the computer, plugged the USB into both the motherboard and the CPU block and now the computer won't show a display once the Windows logo has finished showing. Just black, and my monitor says 'No signal detected'. Only since I tried plugging in the H80i. Honestly this cooler has been nothing but trouble - it's completely corrupted a windows installation before when the firmware installer crashed half way through and caused a blue screen and I then couldn't get windows to turn on.
Any ideas folks?