Data adapter setting removed from report whenever preview is run

Since upgrading to 6.1.1 Final, a report that worked no longer retrieves data when Preview is run - "Document is empty" is returned.  Looking at the report's Dataset and Query Dialog, the data adapter is being reset to "No Data Adapter".  Setting it and testing is sucessful, saving it seems to work.  Exiting Studio and re-entering shows that the data adapter selection is being saved, yet when Preview is run, it is reset to "No Data Adapter" and "Document is empty" is returned.