I previously posted related question in Office Developer Add-in group... http://www.microsoft.com/office/community/en-us/default.mspx?dg=microsoft.public.office.developer.com.add_ins&mid=869e5007-3e31-46be-9d2a-f24ed5a324c8 ....but I did not get any response, so I have reframed a more general question here. In one particular environment (Terminal Services session on MS windows server 2003 standard edition SP2 with Office Professional Plus 2007 SP2), when I try to save a file (programmatically) withOUT .docx extension, the file is automatically saved with the extension. (The file I opened had a name withOUT an extension.) I have run this code in many environments before, including others that seem to be set up like this one, and the file saved successfully without the extension. One additional note: when I do SaveAs, Office always adds the extension, no matter what environment I run in. Could this be the result of a policy setting? (Disclaimer - I know almost nothing about policy settings.) I have looked through the ADM template spreadsheet but I did not see anything that quite matched this situation.