PHASE I (patients with relapsed, refractory, or residual CD20+ non-Hodgkin lymphoma [closed to accrual as of 10/29/07]): Patients receive rituximab IV on days 1, 8 and 15, agatolimod sodium IV over 2 hours on days 6, 13, 20, and 27, and yttrium Y 90 ibritumomab tiuxetan* IV over 10 minutes on day 15 in the absence of disease progression and unacceptable toxicity.