Air conditioning blows but no cool air on 2004 BMW X5

So far my air conditioning has been great since I got the vehicle in late 2008. Just Monday morning, my air conditioner STOPPED blowing cool/cold air! It continues to blow when I turn it on; its just not cold anymore. What could be the problem? (My mechanic believes it could be an electrical problem)

Asked by for the 2004 BMW X5
could be a leak in the system,