Both the Logitech programm and Skype were working fine.
I had a virus problem, which was resolved without a reinstall.
I now find that although Skype is working fine with the webcam, the Logitech programme is not available.
The Logitech Vid HD Icon in the taskbar is greyed out. when I right click on it and "Show Window" the window opens with the Message "Logitech Vid HD was not able to connect properly"
When I click on "Settings - applications and device settings" the Logitech Webcam opens fine with the Settings controls.
I have uninstalled and reinstalled without success.