I have discovered the Driver is often removed and replaced by a Zoom device driver which causes the DPH-50U to fail.
The fix is to locate the Zoom driver and uninstall it, then install the D-Link device. You must be vigilant to not allow Windows to re-install else you will fail again.
I think this is due to this D-Link driver being unregistered with Vista, and the Zoom device is.
Hope this helps another user to use the DPH-50U as intended with Skype.
