If you are found to be eligible to take part in this study, you will receive rituximab through a needle into your vein 1 time a week in Cycle 1. You will not receive rituximab during Cycle 2, but you will continue to take lenalidomide.You will receive a dose of rituximab by vein on Day 1 of Cycles 3-12. Your first dose of rituximab will be given over 6-8 hours. If the first dose is well tolerated, you may receive the next doses over 2-4 hours. If the doctor thinks it is needed, the next doses may given over a longer time.