I posted this verbatim from another thread, but I believe the approach will work for you:
The only troubleshooting step I can think of is to remove any old/stale USB devices and force Windows to re-detect them after an unplug/reboot/replug ... You may do that with USBDeview:
http://www.nirsoft.net/utils/usb_devices_view.html
Sometimes when I install a particular Windows Update or install a new DisplayLink driver, the previous USB drivers/detection logic will break because of stale/conflicting devices. When this happens, I would not be able to get any screen output, but perhaps network/audio from the hub. Try getting rid of (removing) the stale/old USB devices, especially all the ones relating to the DisplayLink hub. Next, reboot the PC. Finally, re-plug the hub. You should see USB detection happen for all the DisplayLink pieces again and hopefully your problem will be fixed.