The purpose of the phase 2 component of this study is to determine if giving the immune molecule NPC-1C to individuals who have cancer of the pancreas or gastrointestinal tract (colon or rectum) which has not responded to standard treatments can shrink or halt the growth of cancer, and to obtain additional data to study its effect on the immune system. Safety data will also be accumulated and evaluated during this study. NPC-1C is a monoclonal antibody that recognizes a specific tumor target on certain cancers. In laboratory studies, the antibody killed tumor cells in some colon and pancreatic cancers that express the NPC-1C antigen by a process called "antibody-dependent cell cytotoxicity" or ADCC.