I've some problem with my usb 3.0 and an external HD. Both works fine because if I plug my external HD to the usb 2.0 all works ok, and If I plug a memory stick to the usb 3.0 all works ok.
USB 3.0 + HD = BAD
USB 2.0 + HD = OK
USB 3.0 + MEMORY STICK = OK
USB 2.0 + MEMORY STICK = OK
...do you have some ideas?