An intravenous (IV) catheter (flexible tube inserted into a vein) is placed in a large vein of the patient's neck, chest or arm for infusion of 5-azacytidine at a constant rate over 4 days. Patients who do not respond to this first dose of 5-azacytidine will be given the drug again after about 50 days. If they do not respond to the second dose, alternate treatments will have to be considered. Patients who respond to 5-azacytidine will begin taking phenylbutyrate on the 14th day after 5-azacytidine was started. They will take about 10 large pills 3 times a day, continuing for as long as the treatment is beneficial. All patients will be hospitalized for at least 6 days starting with the beginning of 5-azacytidine therapy. Those who are well enough may then be discharged and continue treatment as an outpatient.