Thank you, Tobias. I submitted a support request back during this same week. Indeed, these were old DocuWare 5 documents, but the original XML file headers were not "lost" ... they were still there. Nobody could figure it out so we just deleted the old documents that were affected instead of troubleshooting this.
1. Create a 32 bit ODBC DSN connection to the database (ODBCAD32.exe).
2. Open DocuWare Administration and register the connection (under database connections).
3. Create a 64 bit ODBC connection with EXACTLY the SAME name as the 32 bit ODBC connection (ODBC Data Sources 64 bit).