can i be fired if i am on short term disability.?

i am a truck driver and have been taken out of work by the MIDOT and my company has all the paper work to prove this, however they are talking about terminating me because I have been out of work for longer then 30 days. On the paper work it says that I am to be out for six months, which puts me back to work on the 18th of Feb. 2007. Can you help me with this problem, I want to know if they can leagally do this.