I. To determine the maximum tolerated dose of CpG 7909 that can be delivered in four doses (days 6, 13, 20, 27) for patients with relapsed CD20+ non-Hodgkin's lymphoma. (Phase I) II. To assess the toxicity of CpG 7909 when combined with rituximab and Y-90 Zevalin in patients with lymphoma. (Phase I) III. To assess the overall response rate (CR + PR) of this regimen in relapsed diffuse large B cell lymphoma. (Phase II) IV. To assess the toxicity of the treatment regimen in patients with relapsed diffuse large B cell lymphoma. (Phase II) V. To assess the time to progression and duration of response in patients with relapsed diffuse large B cell lymphoma. (Phase II)