 VELCADE is approved by the Food and Drug Administration FDA for the treatment of multiple myeloma in patients who have received at least two prior therapies and have demonstrated disease progression on their last therapy. Its effectiveness is also being tested in other cancers. The dose of the drug being used in this research study is the same as what is used for the treatment of multiple myeloma. It has not been approved by the FDA for use in GVHD. Therefore, using VELCADE for GVHD is experimental in this research study. 