I had this trouble with my 2004 -- the ESB/ABS light would come on more and more frequently and would stay on...no apparent mechanical problems EXCEPT occasionally the autostick would not shift out of Park.

Took it in to dealer and they replaced a $35 switch (the one that "tells" the autostick the brake is depressed) for $250. It was not covered by my MAX CARE warranty. But it cleared up the problem.