Hi,
This was an issue with Workstation 8.x as well, the same happened to me. My host PC was Win 7 though, but after I plugged my blackberry into the USB to test it under Win 8(it was about to be released), it installed some drivers on the host as well and from then all of my USB periferials shut down, no power nothing. even after reboot. The only thing I could do is to remove Workstation and then remove all the usb hubs from device manager to make the host Win re initialize again. Then it was fixed.
Cheers