what sort of rice did you use? If it was the standard long grain rice, that will damage the burrs as it is too hard. I think the HB recommended rice is 2 minute rice, which is a lot softer than normal rice.
Heres a link to a similar tale of woe from another CSr.
All the best.
P.S. I think the general concensus on this forum is not to put anything in your grinder that isnt coffee.