Delta MW9001 light comes and turntable turns when switched on at the wall ?

I have recently bought a Delta MW9001 microwave oven from Aldi. It was working well for some weeks, but now the interior light comes on imediately when it is switched on, and the turntable turns, but it will not accept any time set in the display and just beeps when start is pressed. It seems as if it needs a factory reset but I don't know how to do this. Has anybody got any Idea how to fix this problem?

Rob
July 2008