I have 3 VMs with 4 drives in a VS running without a hitch for some time now.
For the first time ever, I inserted a usb flash drive into the host. It
failed to show up on "my computer". When checked, the drive device was
present. On a hunch, I disconnected the VMs, and the usb drive was found by
"my computer". I then removed the usb drive, and reconnected the VMs (with
the original drive letters), and the usb drive continues to be found.