Had a similar issue once and it turned out to be a powered USB hub backfeeding and putting the motherboard into an odd power state, only figured it out when I noticed a status LED remaining on after I physically unplugged the main power for the computer. May be worth unplugging any hubs you may have to rule that out
Had a similar issue once and it turned out to be a powered USB hub backfeeding and putting the motherboard into an odd power state, only figured it out when I noticed a status LED remaining on after I physically unplugged the main power for the computer. May be worth unplugging any hubs you may have to rule that out