 This study will evaluate the side effects of a fixed dose of vaccine and GM-CSF with increasing doses of anti-CTLA-4 antibody in patients with advanced prostate cancer. The vaccine consists of a priming vaccine called PROSTVACTRICOM, made from vaccinia virus, and a boosting vaccine called PROSTVAC-FTRICOM, made from fowlpox virus. GM-CSF is a chemical that boosts the immune system, and anti-CTLA-4 antibody is a protein that may improve anti-tumor activity and the response to the vaccines. DNA is inserted into the priming and boosting vaccine viruses to cause production of proteins that enhance immune activity and also to produce prostate specific antigen PSA-a protein that is normally produced by the patients tumor cells. 