Inclusion Criteria:

- Subject, parent, or legal guardian provided written informed consent.

- Subjects must be >6 months and <21 years of age.

- Subjects must have one or two available 4, 5, or 6/6 antigen matching unrelated UCB
unit(s) that will deliver a cell dose between 3.0-5.0 x 107cells/kg.

- These units must be HLA-matched minimally at 4 of 6 HLA-A and B (at intermediate
resolution by molecular typing) and DRB1 (at high resolution by molecular
typing) loci with the subject.

- If two CB units will be used, the units must be HLA-matched at 3 of 6 HLA- A, B,
and DRB1 loci with each other (using same resolution of molecular typing as
indicated above).

- For a single unit transplant, a minimum of 3 x 107cells/kg will be required.

- For a double unit transplant, HLA-matched units must be available such that
together both units deliver a combined pre-cryopreserved nucleated cell dose of
at least 4.0 x 107 cells/kg with 1 unit of at least 2.5 x 107 cells/kg and the
other at least 1.5 x 107 cells/kg.

- Subjects must have histologically confirmed diagnosis of a hematologic malignancy or
a laboratory confirmed inherited metabolic disease.

- Subjects who have had a prior autologous or allogeneic transplant are allowed to
participate provided it has been >1 year since the transplant was completed.

- Subjects must not have active CNS disease at the time of study enrollment.

- Subjects must have a life expectancy of >4 months.

- Female subjects capable of reproduction (defined as a subject who has started menses)
must agree to the following:

- Use of an effective oral or IM contraceptive method during the course of the
study and 2 months following the last administration of study drug.

- Female subjects capable of reproduction must have a negative pregnancy test
result within 3 days prior to first study drug dose.

- Subjects must have adequate function of other organ systems as measured by:

- Creatinine <2.0 mg/dL and creatinine clearance >50 mL/min.

- Hepatic transaminases (ALT/AST) <4 x ULN, bilirubin <2.0 mg/dL.

- Adequate cardiac function by echocardiogram or MUGA scan (ejection fraction or
shortening fraction >80% of normal value for age).

- Pulmonary function tests demonstrating FVC and FEV1 of >60% of predicted. DLCO
should be used for subjects >10 years old. Crying vital capacity of >60% may be
substituted for subjects unable to complete PFTs.

Exclusion Criteria:

- Subjects with an uncontrolled infection at the time of cytoreduction.

- Subjects who are pregnant or breast feeding.

- Subjects who are known to be seropositive for HIV or HTLV-1.

- Subjects who have had an autologous or allogeneic transplant <1 year from the
anticipated administration of the first dose of study drug.

- Subjects who have received treatment with an investigational agent within 30 days of
anticipated administration of the first dose of study drug.

- Subjects with current alcohol use, illicit drug use or any other condition (e.g.,
psychiatric disorder) that, in the opinion of the Investigator, may interfere with
the subject's ability to comply with the study requirements or visit schedule.

- Subjects must not have any co-morbid condition which, in the view of the Principal
Investigators, renders the subject at too high a risk from treatment complications
and regimen-related morbidity/mortality.