Either the drive or the particular usb keyboard you have is a current level grabber in that it pulls down the usb bus! I have a gaming model illuminated keyboard that has to go into a port directly for that reason and use a usb hub with a separalte ac adapter for things like flash drives to have the adequate current available.
This had been a problem with the last build and so far hasn't been checked on the new one while the same hub is also convenient as well!
But the keyboard pulls too much to even use a PS/2 adapter and not light up at all. I'm stuck plugging in a second roll away type keyboard just to press F12 at post to bring the boot device menu up as well.
I've plugged different flash drives(have several, different brands) directly into the ports on the old build and they all refused to boot from when turned into a live usb stick for some reason due to this. CyberPower makes some small 4 port hubs with a blue led and amber when a device/drive is plugged in that have been found quite reliable on the other hand for solving this type of problem. Cyberpower Systems USA, Inc. 4-Port USB 2.0 Hub CPH420P
Those are commonly seen in Walmarts at times or were, Radio Shack, and found for less online. But for a small hub they last! Keep the keyboard plugged in direct while plugging various brand flash drives into one of these. That so far has worked out well here with different sized as well as different brands.
(best price = http://www.buy.com/prod/cyberpower-u...203268227.html