A Phase I Trial of Myeloablative Conditioning w/ Clofarabine and HD Busulfan for Pts w/ Refractory Heme Malignancies Undergoing Allo PBSCT

Inclusion Criteria: * Documentation of disease. Patients must have one of the following disease types: * Acute myeloid leukemia (AML) with either: * Primary refractory to induction chemotherapy * Relapsed and refractory AML with \>5% blasts in bone marrow or extramedullary disease (excluding active disease of the central nervous system). * Patients in second or subsequent complete remission (CR2, CR3, etc.). * Acute lymphoblastic leukemia (ALL) with one of the following criteria: * Primary refractory to induction chemotherapy. * Relapsed and refractory ALL with \>5% blasts in bone marrow or extramedullary disease (excluding active disease of the central nervous system). * Patients in second or subsequent complete remission (CR2, CR3, etc.). * Myelodysplasia, refractory anemia with excess blasts with 11-20% blasts in the bone marrow (RAEB II). * Chronic myelogenous leukemia (CML) with one of the following criteria: * Accelerated phase. * Patients in blast crisis. * Patients with aggressive non-Hodgkin's lymphoma (NHL), including diffuse large cell lymphoma, mediastinal B-cell lymphoma, transformed lymphoma, mantle cell lymphoma, and peripheral T cell lymphoma, who also have one of the following criteria: * Failure to achieve complete remission to primary induction therapy * Relapsed NHL, refractory to at least one line of salvage systemic therapy * Patients who relapse \< 6 months following autologous stem cell transplantation are not eligible. * Patient age 18-60 years * Availability of a consenting HLA-matched donor * Performance status ECOG 0-1 * No active infection. Patients with active infections requiring oral or intravenous antibiotics are not eligible for enrollment until resolution of infection. * No HIV disease. Patients with immune dysfunction are at a significantly higher risk of infection from intensive immunosuppressive therapies. * Non-pregnant and non-nursing. Treatment under this protocol would expose a fetus to significant risks. Women of childbearing potential should have a negative pregnancy test prior to study entry. Women and men of reproductive potential should agree to use an appropriate method of birth control throughout their participation in this study due to the teratogenic potential of the therapy utilized in this trial. Appropriate methods of birth control include oral contraceptives, implantable hormonal contraceptives (Norplant®), or double barrier method (diaphragm plus condom). * Required baseline laboratory values: * LVEF \> 45% corrected * DLCO \> 50% of predicted value (corrected for hemoglobin) * Serum creatinine ≤ 2.0 mg/dl or estimated creatinine clearance of ≥60 ml/min * Bilirubin \< 1 x upper limit of normal value * AST and ALT \< 1 x upper limit of normal value * Signed written informed consent. Patient must be capable of understanding the investigational nature of the investigational nature, potential risks and benefits of the study, and able to provide valid informed consent. Exclusion Criteria: * Patients who relapse \< 6 months following autologous stem cell transplantation are not eligible