Vintafolide is a drug that is specifically designed to enter cancer cells via the folate vitamin receptor (FR). Experimental evidence shows that this target receptor is expressed on virtually all ovarian cancers as well as the majority of endometrial cancers. Early clinical evidence in a small number of Phase I patients suggests that vintafolide may have antitumor effect in women with advanced ovarian cancer and that it is generally well-tolerated. This evidence suggests that vintafolide may be useful as chemotherapy against advanced ovarian and endometrial cancers. The primary objective of Part A of this study is to collect data on clinical benefit produced by therapy with vintafolide. The primary objective of Part B of this study is to collect data on the safety and efficacy of vintafolide.