OK, despite the same symbol being used to label the Audio Out on the mini, I appear to have the cable/Apple Mini Display adaptor that provides video out to a VGA monitor via the Thunderbolt port.
What's with the multiple meanings of the same symbol?!
[attachment=3537:Mac_mini...maller_2.gif]
The box between 2 vertical lines is for audio in/out.
[attachment=3538:Apple_Adaptor.gif]
The Apple adaptor with the same icon
There is a chance that the problem is the mini Display port, but I don't have a HDMI to VGA adaptor...