Inclusion Criteria:

- Histologically confirmed malignancy, including the following types:

- Hematologic malignancy, including any of the following: (Accrual for patients
with hematologic malignancies temporarily closed as of 11/30/04)

- Mantle cell lymphoma

- Morphologically confirmed disease

- CD20 and CD5 positive

- Any other refractory lymphoma

- Chronic lymphocytic leukemia

- Rai stage III or IV and meeting at least 1 of the following criteria for active
disease:

- Weight loss > 10% in the last 6 months

- Fatigue

- Fever or night sweats with no evidence of infection

- Progressive anemia or thrombocytopenia

- Progressive lymphocytosis with a lymphocyte doubling time of < 6 months

- Marked hypogammaglobulinemia or paraproteinemia

- Progressive splenomegaly and/or lymphadenopathy

- Multiple myeloma

- Disease confirmed by bone marrow aspirate and/or biopsy

- Relapsed or refractory disease after the most recent treatment regimen

- Quantifiable monoclonal immunoglobulin in serum and/or urine

- Solid tumor, including but not limited to any of the following:

- Breast cancer

- Histologically or cytologically confirmed stage IV invasive disease

- HER-2 positivity not required for study enrollment

- Tumor overexpressing HER-2 should be confirmed by immunohistochemistry OR
fluorescence in situ hybridization

- Small cell lung cancer

- Extensive stage or limited stage disease in relapse

- Extrapulmonary small cell carcinoma allowed

- Squamous cell carcinoma of the head and neck

- Metastatic, recurrent, or refractory disease

- Renal cell carcinoma

- Mesothelioma

- Pleural or peritoneal disease of epithelial, sarcomatoid, or mixed subtype

- Melanoma

- Kaposi's sarcoma

- Metastatic or unresectable disease for which standard therapy does not exist or
is no longer effective

- Measurable or nonmeasurable disease (solid tumor patients)

- Measurable disease defined as at least 1 unidimensionally measurable lesion ≥ 20
mm by conventional techniques or 10 mm by spiral CT scan

- Nonmeasurable disease includes any of the following:

- All other lesions, including lesions < 20 mm by conventional techniques or 10 mm
by spiral CT scan

- Bone lesions

- Cytologically positive pleural or peritoneal disease

- Elevated tumor marker (e.g., CEA, CA 125, CA 19-9, or other tumor marker)

- Multinodular or confluent nonmeasurable pulmonary, hepatic, adrenal,
intra-abdominal, or skin metastases

- Previously treated with at least 1 chemotherapy regimen*

- Prior therapy may have included combined modality treatment (e.g., full-dose
chemotherapy and radiotherapy with radiosensitizing chemotherapy)

- Prior therapy with flavopiridol allowed provided the patient was enrolled in a
flavopiridol clinical trial employing a different schedule NOTE: *Except in
cases where chemotherapy is not known to be effective (e.g., renal cell
carcinoma, chondrosarcoma, or gastrointestinal stromal tumor)

- No active CNS metastases

- History of CNS metastases allowed provided all of the following criteria are met:

- Previously treated and stable and asymptomatic for at least 4 weeks since the
completion of treatment

- Image documentation required

- Off steroids or on a stable dose of steroids for at least 1 week

- Hormone receptor status:

- Not specified

- Age

- 18 and over

- Sex

- Male or female

- Menopausal status

- Not specified

- Performance status

- ECOG 0-1 OR

- Karnofsky 70-100%

- Life expectancy

- More than 12 weeks

- Hematopoietic

- Absolute neutrophil count > 1,000/mm^3*

- Platelet count > 75,000/mm^3 (50,000 for hematologic malignancies)* (Accrual for
patients with hematologic malignancies temporarily closed as of 11/30/04) NOTE:
*Unless abnormality is caused by tumor burden and not cumulative prior
chemotherapy

- Hepatic

- Bilirubin normal

- AST/ALT ≤ 2.5 times upper limit of normal (ULN) (5 times ULN if liver metastases
are present)

- Renal

- Creatinine ≤ 2.0 mg/dL OR

- Creatinine clearance ≥ 60 mL/min

- Cardiovascular

- No myocardial infarction within the past 6 months

- No unstable angina within the past 6 months

- No transient ischemic attack or cerebrovascular accident within the past 6
months

- No history of arterial vascular events

- No new cardiac arrhythmias likely to be related to cardiac ischemia within the
past 6 months

- No symptomatic congestive heart failure

- Pulmonary

- No history of pulmonary embolism within the past 6 months

- Gastrointestinal

- No chronic diarrheal disease within the past 6 months

- No severe malnutrition

- No intractable emesis

- Other

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective hormonal or barrier contraception

- No ongoing or active infection

- No other concurrent uncontrolled illness

- No psychiatric illness or social situation that would preclude study compliance

- At least 3 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin)

- At least 3 weeks since prior radiotherapy No prior radiotherapy to 50% or more of
bone marrow

- Recovered from all prior therapy No other concurrent investigational agents No
concurrent combination antiretroviral therapy for HIV-positive patients