 INDUCTION THERAPY: Patients receive clofarabine intravenously IV over 1 hour and cytarabine hydrochloride IV over 2 hours on days 1-5. Patients receive an infusion of non-HLA matched ex vivo expanded cord blood progenitors on day 6. Filgrastim G-CSF is administered subcutaneously SC on days 0-5 and from day 7 until blood counts recover. Treatment modifications may apply according to response. 