I've tried to install the Intel driver manually: there are two family driver I find some discussions, but nothing has solved my problem. The USB 3.0 works properly pluged to another pc ('pure' Windows), so USB 3.0 drive isn't damage.
I've two external drive, one USB 2.0 and the other USB 3.0.
I've a iMac (Dic 2013, Intel i7-4771), through boot camp assistant I've installed Win 7.