Sounds like it may just be busted. If it was stuck, and nothing was spinning, I'd say click on the link in my signature. But if the 1/10 wheel is spinning, then it sounds like something may have broken internally.
A registered Speedo shop may be your best bet.
My oil line fix
My 100k stopped odometer fix
Brace for impact, I'm in a "modifying mood". Massive thread count inbound.