This is a research study because the study drug, dasatinib (Sprycel®), has not been evaluated for safety or effectiveness in patients with hormone-refractory prostate cancer. The drug is approved by the Food and Drug Administration for treatment of some forms of leukemia; thus, dasatinib (Sprycel®) is not an investigational drug. It has been given safely to hundreds of patients already. However its safety and usefulness in this study population (prostate cancer) is unknown.