(Juggler @ Apr. 22 2007,19:13) Your speedo sensor nut may be loose. Be careful as mine worked it's way out, and cracked the cover from the inside. From what I hear, it's relatively common as the dealer doesn't look at it when they prep the bike.
In order to check, you'll most likely need to take off the cover. It helps if the left hand side plastic is off. You can get it off without taking the plastic off, but it's a pain. It covers the counter-sprocket that the chain goes over on the front.
Good luck.