The purpose of this study is to determine the safest dose of XL999 and how well subjects with Non-Small-Cell Lung Cancer tolerate XL999. XL999 is a small molecule inhibitor of multiple kinases including VEGFR, PDGFR, FGFR, FLT-3, and Src, which are involved in tumor cell growth, formation of new blood vessels (angiogenesis), and metastasis.