speedometer needle (but not odometer!) stuck

[Atlus]

Hey everybody, the needle on my speedometer of my 2003 gz250 has recently froze and now simple bounces around in the 0-5mph range. This happened around last tuesday while I was driving to class. Basically when I started getting to around 15-20 mph the needle started twitching a dropping back down to zero. At first it would start up again when I started my bike but the same problem would repeat and now the needle is simply no longer moving. I know the cable is still good since I took it out and it still rotates when I push the bike and both the trip and total odometer seem to be working fine. Any suggestions on what the problem could be and how to fix it? Thanks!!! :??:
-Alex