Gene therapy is a very new medical technique being used in a number of clinical studies for diseases such as cancer and cystic fibrosis. In this study, a novel bioengineered lenti viral vector will be used to deliver a normal gene for human clotting FVIII or FIX into patients with hemophilia A or hemophilia B. This study is a Phase I/II trial evaluating the safety efficacy and pharmacokinetics of IV infusion of gene modified autoHST in patients with hemophilia A or hemophilia B.