This phase II trial studies how well giving docetaxel and lapatinib ditosylate together as second-line therapy works in treating patients with stage IV bladder cancer that cannot be removed by surgery. Drugs used in chemotherapy, such as docetaxel, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Lapatinib ditosylate may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Giving docetaxel and lapatinib ditosylate together may kill more tumor cells.