No yellow triangles in devices and a 'no entry' sign, are leading me to think that perhaps it is the program being used with the camera, rather than the camera itself. Try using the camera with a different program, or re-install the program - I am thinking along the lines of something like Skype or MSN Messenger etc.
No clues in there either. The only controls for the webcam seem to be within the 'Play Camera' software, and there is no option to turn the thing on and off, just change the resolution, colour balance, file locations etc.
What happens if you launch the Play Camera thing on yours??
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