Patients with B-cell lymphoma who relapse after autologous transplant tend to have a poor prognosis. Currently, there is no standard treatment for such patients. Bexxar is a radioactive antibody therapy that has shown a 60-80% response rate in non-transplanted patients with relapsed B-cell lymphoma. This study will test the safety and efficacy of Bexxar in the treatment of patients whose B-cell lymphoma has relapsed after an autologous transplant.