The goal of this study is to evaluate a new approach to immunotherapy in NHL by combining two antibodies, veltuzumab and epratuzumab. For treatment, epratuzumab has also been attached to a radioactive isotope called 90yttrium (90Y-epratuzumab). Veltuzumab and 90Y-epratuzumab attack different areas on lymphoma cells. Because of this, treatment with the combination may provide more effective treatment in NHL than either veltuzumab or 90Y-epratuzumab given alone.