This study will examine the safety and toxicities of intravenously administering a genetically modified type of Salmonella bacteria (VNP20009) and its impact on tumor growth in advanced or metastatic cancer (cancer that has spread from the primary site). The first patients in the study will be given the smallest dose of VNP20009, and those who enter later will receive increasingly larger doses. This will be done to determine the maximum dose that can be given without serious side effects.