sillygrendel once bubbled...
Mine wouldn't strike for one of the night dives in Bonaire. It was two days before I decided to take apart the lighthead and have a look. Like O-ring said, I used scouts for two night dives because of it.
The bezel was a little bit loose which might have caused the striking problems. I took it apart. Let everything sit out for 12hrs, made sure it was clean and put it back together. Worked fine for the rest of the trip.
It could have been worse. It could have completely flooded and the bulb could have broken.
I'm still not quite sure how the bezel became loose. I should really blame myself for not checking before the dive - I just didn't think of it as I'd used it 7-8 time before without problems, including on that trip.