The main purpose of this study is to determine the effects (good and bad) and the safety of Dynavax's immunostimulatory phosphorothiolate oligodeoxyribonucleotide (1018 ISS) given in combination with Rituxan on patients with B-cell follicular non-Hodgkin's lymphoma. This research is being done because recurrent follicular non-Hodgkin's lymphoma is not curable with standard chemotherapy or antibody treatments. 1018 ISS is an experimental compound that consists of short pieces of DNA that stimulate the immune system. It is hoped that 1018 ISS may improve the ability of Rituxan to kill cancer cells.