PX 866 is a new type of drug that inhibits a molecule related to cancer cell growth. While this molecule is also found in normal cells, it is much more active in some cancer cells, so inhibiting the molecule with PX-866 is hoped to slow the growth of cancer cells. Laboratory tests show that it may help slow the growth of prostate cancer in animals, but it is not known whether it will have the same effects in humans. PX-866 has been studied in some cancer patients to find out safe doses that can be given but it has not undergone study in prostate cancer. This study will be the first study of PX-866 in prostate cancer.