my dads old beemer had this problem, the car had been standing for a long time on the forecourt before he bought it... i presumed it had dryed up or something so i manged (JUST) to get some oil on the workings and its still sticks a bit, but not that much now. a way to tell if its this is to reset the trip meter. if it clocks up milage but no speed then its still working but the needle is stuck, maybe you can sort it yourself?? if not, does it stick at a certain speed? maybe its an error code for something? my mates bike got stuck at 55mph as soon as the ignition came on. this was error for throttle position sensor lol!
hope this helps.
PS: 500+ for a speedo!!!! bliiiiiiiiiiiiiiimy