The durg vorinostat (Zolinza) is a type of drug called an histone deacetylase (HDAC) inhibitor. It inhibits a group of enzymes called histone deacetylases. These enzymes help cancer cells survive. By inhibiting these enzymes, vorinostat helps kill cancer cells. In this research study vorinostat will be given along with radiation therapy and the drug 5-FU. This is the first research study in which vorinostat will be given along with radiation therapy and 5-FU. The purpose of this research study is to find the highest dose of vorinostat that can be given safely along with radiation therapy and 5-FU. The investigators will also begin to get information about whether vorinostat combined with radiation and 5-FU may help to treat pancreatic cancer.