USBs are funny creatures. First thing I'd try is to shut down PC then connect the webcam to the port giving trouble. Reboot and see what happens.
Legacy drivers do corrupt at times even more so if you don't use the safely remove wizard if showing in the notification area even if the peripheral is hot plug and play.
This is quite a small and powerful program that you can use for USB problems but I advise caution and to read the help files. Please use at your own risk.