This is an open label study combining Rituxan and SDX-105. Rituxan will be given on day 1 followed by a 30-60 minute intravenous infusion of SDX-105 on day 2 and day 3. Treatment will repeat every 21 days (a cycle). Treatment can continue for up to 6 cycles (about 4 months) if tumor status improves and there are no unacceptable side effects. Patients will be followed for up to 2 years or until disease progression.