Maybe your black co-workers are just fearful that when Obama screws up (as he will) the screw up will have racial connotations. He will be, after all, the first black president.
Very astute of you. I said something similar to a black friend: it's unfortunate for the sake of future racial relations and the progress of African-Americans in this country that the first black man elected president is not a competent person. He may poison the well for other blacks for a long time. She agreed.