<qa>  What is the best dose of alvocidib?This phase I trial studies the side effects, best way to give, and the best dose of alvocidib when given together with fludarabine phosphate and rituximab in treating patients with previously untreated or relapsed lymphoproliferative disorders or mantle cell lymphoma. Monoclonal antibodies such as rituximab can locate cancer cells and either kill them or deliver cancer-killing substances to them without harming normal cells. Drugs used in chemotherapy such as alvocidib and fludarabine use different ways to stop cancer cells from dividing so they stop growing or die. Combining monoclonal antibody therapy with chemotherapy may kill more cancer cells. 