One night just as I became visual on an ILS, I switched on the landing light and all the panel lights went out.
Hmm, similar thing happened to me once. Except it was on take off in a twin, at night in fog / very low marine layer (which had rolled in damn quick). Down the runway, rotate and into the fog, gear up, and the panel lights went out.
The moral of that story is always have a torch very ready! By the time we got some light onto the instruments we were banked 30 or so degrees to the left...
Now I carry one clipped to my headset, and always on for critical phases of flight at night
EA