Several dose levels of erlotinib and pralatrexate will be tested. Three (3) to 6 participants will start at the lowest planned doses of erlotinib and pralatrexate. Each new group of 3-6 participants will receive a higher dose than the group before it, if no intolerable side effects were seen. This will continue until the highest tolerable dose of erlotinib in combination with pralatrexate is found.