DISEASE CHARACTERISTICS: Pathologically proven advanced solid tumors for which no standard therapy exists or that has progressed or recurred following prior therapy Measurable or evaluable disease No hematological malignancies (e.g., leukemia or lymphoma) No known brain or leptomeningeal disease, unless lesions were previously irradiated, currently not being treated with corticosteroids, and have no clinical symptoms

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9 g/dL Hepatic: Bilirubin less than 1.5 mg/dL AST or ALT no greater than 2 times upper limit of normal (ULN) (no greater than 5 times ULN if due to tumor) PT and aPTT no greater than 1.5 times ULN Renal: Creatinine no greater than 1.5 mg/dL Creatinine clearance at least 60 mL/min Cardiovascular: No unstable atrial or ventricular arrhythmias that require medication No ischemic events within 6 months Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No psychiatric disorders No history of seizure disorders No other severe concurrent disease No history of ulcers or abnormalities that would interfere with carbendazim absorption No history of hypersensitivity to PEG-formulated medications (including cyclosporine or etoposide)

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks since prior nitrosoureas or mitomycin) and recovered No concurrent cytotoxic therapy Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy Surgery: No prior gastrointestinal surgery that would interfere with carbendazim absorption Other: No concurrent use of phenytoin, phenobarbital, valproic acid, or other antiepileptic prophylaxis No concurrent scheduled antacids, such as H2 blockers (e.g., cimetidine or ranitidine) or hydrogen pump inhibitors (e.g., omeprazole), or cisapride