Veliparib and Temozolomide in Treating Patients With Recurrent Glioblastoma

RATIONALE: Veliparib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Drugs used in chemotherapy, such as temozolomide. work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving veliparib together with temozolomide may kill more tumor cells. PURPOSE: This randomized phase I/II trial is studying the side effects and best dose of giving veliparib together with temozolomide and to see how well it works in treating patients with recurrent glioblastoma.