Something stupid like the radio earthing through the arial :?
The interior light on the TDI poacked up months ago (engine's been in piece for months too) and when it went, all the lights stayed on for 10 minutes then timed out and now won't come un unless I pull the fuse out for a second, then the same, on for 10 minutes.
Might be worth checking the same hasn't happened ie a short somewhere that makes the lights thing they are on permenantly.