I had the same problem with my 05. I sprayed several different types of cleaner or lube through the outside of the switch and it did no good. I finally broke down and removed the switch, cleaned and lubed, now it works like new. I used Fred's step by step for fixing a reverse switch and it was a great help. I had a little trouble snapping all the switch parts back together, but after a few attempts I finally got it (Wife helped).
If you want to R&R, the handlebar comes of with 2 bolts (Thanks Waldo) and makes removal of the switch housing much easier.
Good luck.