Chuck,
The same behaviour happened on my AVL, but I hadn't swapped the bulb. The red wire connected to the the bulb was frayed. It routes out the back of the nacelle and is exposed and I think the elements took their toll. The blue and green one route inside the nacelle and are wrapped in sheath, so maybe they are better protected.
Take a look in there and follow that red wire. See if it's been chewed up a bit. If you turn your handlebars to the right, you should be able to see the red wire on the left side, but you will probably have to pull the headlight off.
Boggy