Yep, had this several times. If you take the back panel off (the small sub panel that covers the bottom left from the back view) you'll probably notice that it's very damp inside. The centre support of the heater coils on mine actually broke in the middle and shorted the coils out against the silver reflector strips. Hopefully yours won't be that serious and just need drying out. However if it is that bad, you'll need to first dry it out thoroughly and then get hold of some sticky backed high temperate woven fibreglass tape (it's a pure woven tape, not a clear tape with woven fabric in it) and wrap some around the reflector strips where there is likely to be any shorts of the coils. Hopefully this should cure it.
You'll probably find that engineers aren't too hot at solving this problem either!
Damien Beale, December 2007