I have a usb hub with some usb2.0 ports and some usb3.0 ports on it. It is plugged into a retina mbp into one of the usb 3.0 ports. There is an audio interface plugged in which the macbook see, and a wacom tablet and also a usb2.0 HDD. however it is not seeing either of my WD ultra HD's which are both usb 3.0 they work ok if plugged directly into the usb port on the mac. It has been working fine up until recently. Although I had a similar problem some time ago but it fixed itself. The ports on the hub seem Ok as I've tried other peripherals in the ports. I have reset the pram and also the smc, but I was wondering if there is some other usb controller settings somewhere that I can reset or some cache I can trash. thanks.