You can't identify root hubs easily, usually 2 connectors share the same root hub, so moving to a free other connector is a good tactic. I am sure, the connector you have used before is shared with one that has other devices attached.
I am having the same problem as well. The Virus Audio driver shows a "Code 10. The Device can not start." I am on Windows Vista Ultimate 64. RME Multiface Soundcard. Also when the software installs it does not install the drivers properly. I have to go into device manager, where I can see the Virus TI drivers, but it has a warning that states the driver is not found. I have to manually install the USB and Midi driver. Once I install the USB driver, the Virus Audio driver shows up (version 2.8.31) with the code 10 error.
I have unplugged all other USB devices from my PC, so bandwith should not be an issue. I am using the on board USB. It is a Gigabyte GA-EP45-DS4P motherboard. The USB controller uses an intel ICH10R chipset. The controller is also used for the SATA drives as well as the PCIexpress buss. I have 3 UAD2 cards on the PCI express bus and the computer has 2 hard drives.
I also tested on another system as well as my laptop. I experienced the same problem.
I thought about adding a USB card to my system, but I do not have an open PCI slot and that's the only USB card I can obtain locally. I could order a PCI express USB card, but I really don't want to do that just for testing. Are there compatiblilty issues with different USB controllers?