Well… try the basic troubleshooting stuff.
Does the drive do this on another computer?
What about different USB ports? Some onboard ports are hubs and some are direct.
I’m also assuming (legacy usb support) makes no difference, tried it both ways, right?
I once worked on a system like this, many moons ago, and the only solution was to purchase a USB card. The onboard ports were too buggy for whatever reason. We didn’t investigate too deeply, but it was among the first USB 3.0 implementations.
Another instance required me to kill the power entirely to the system. Removing the main battery, cmos/bios battery, and the ac mains. Only then was the problem fixed. This one was different from your issue in that it would lock up on POST though… if it had USB drives connected.
