have not had problems with Outlook 2003 not exiting but with Xobni neither task (Outlook or Xobni Service) exit when I close Outlook - ever!
Sorry to come in so late on this thread but have you tried using Knockout, Carol? http://sunflowerhead...m/software/knockout/
It will close down Word and Outlook if necessary. To quote the developer (Jensen Harris) "From a notification area icon, KnockOut can show you if Microsoft Outlook and Microsoft Word are running on your computer (even if no windows are showing on your taskbar). If one of these applications is in a hung state, you can terminate them right from the KnockOut menu. This will help clear up rare mystery situations, in which you think Outlook is not running because you see no windows on your taskbar, but when you launch Outlook again nothing happens because it is actually running in the background."
I originally started using it when Outlook 2003 began failing to close properly when hooked up with the outliner, PocketThinker. Recently I have had problems getting Outlook to close down gracefully when used alongside Zoot32. Knockout seems to do the trick, although I'm not clear (I just don't know) if it does it any more safely than would be achieved by using "end task" from the Task Manager.