Arm B: Patients receive low-dose RO4929097 PO once daily on days 1-3, 8-10, and 15-17 and rifampin PO once daily on days 1-10 for course 2 only. For course 3 and beyond, patients receive low-dose RO4929097 on days 1-3, 8-10, and 15-17. Courses repeat every 21 days in the absence of disease progression or unacceptable toxicity.