My first guess was that he had moved from IL to CA, but then something you said about opening the CA return after IL made me think he went in the opposite direction, which I admit isn't a reasonable conclusion.  There may be some hidden box that you have to check on a CA worksheet, but it may be that the program can't deal with that situation.  With only a week remaining, the easiest solution may be to complete the Schedule S the old-fashioned way.