Are you experiencing a dialog box with the following text on attempting to export a Smartlist to Excel?
“RUN APPLICATION ERROR”
"C:\Users\user\AppData\Local\Temp\7\somefilename.xlsx returned 29"
This seems to be an error passed back from Excel regarding permissions issues, or lack of communication to excel from GP via DDE (Dynamic Data Exchange).
The option in excel in advanced options (File>>Options>>Advanced)
“Ignore other applications that use Dynamic Data Exchange (DDE)” should be unchecked.
There are a couple of threads on this on the GP forums: