Riding in an hour of steady rain during which your bike performs flawlessly. Then gently and carefully hosing off the road crud when you get home, only to find you've got something "too wet" and it wont start.
In the shop we used to spray wires down with water while the engine ran and you could hear and see it arc off to a close ground point. If they were real bad it would make the engine stumble or create a dead cyl for a minute.
Might want to try this to see if your wires are breaking down.