ARM I: Patients receive MEK inhibitor MEK162 orally (PO) twice daily (BID) on days 1-14, and leucovorin calcium intravenously (IV) over 2 hours, oxaliplatin IV over 2 hours, and fluorouracil IV continuously over 46 hours on days 1 and 2. Courses repeat every 14 days in the absence of disease progression or unacceptable toxicity.