The purpose of this study is to evaluate the effects of the study drug, BKM120. The study drug, BKM120, is an inhibitor of a protein called phosphatidyl inositol-3-kinase (PI3K). This protein is found in normal cells and in cancer cells, but often in many cancer cells this protein is overactive. Inhibiting the protein may slow the growth of prostate cancer but this has not been tested yet in men with prostate cancer.