
Best guess: there's a dialog box waiting for user input
Check around in the methods for a quieter shutdown operation. I have this issue with Office apps all the time; as Microsoft themselves are fond of saying in several KB articles, Office was never intended for multi-user (i.e. remote, unattended = programmatic) functionality.
Many fears are born of stupidity and ignorance -
Which you should be feeding with rumour and generalisation.
BOfH, 2002 "Episode" 10