PRIMARY OBJECTIVES: I. To determine the response rate by Response Evaluation Criteria In Solid Tumors (RECIST) criteria, prostate-specific antigen (PSA) response by the PSA Working Group criteria, and overall clinical benefit defined by summation of RECIST complete responses (CR) plus RECIST partial responses (PR) plus PSA PRs. SECONDARY OBJECTIVES: I. To determine time to progression in patients with hormone-refractory prostate cancer (HRPC) receiving oxaliplatin and pemetrexed. II. To describe the safety profile of this treatment. III. Pain response will be evaluated in an exploratory manner. IV. Undertake a pilot analysis of excision repair cross-complementing 1 (ERCC1) expression levels and polymorphisms, looking at their ability to predict response to platinum therapy. OUTLINE: Patients receive oxaliplatin intravenously (IV) over 2 hours and pemetrexed disodium IV on day 1. Courses repeat every 21 days for up to 1 year in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 6 months.