Within Outlook 2007, when re-editing a meeting that was just saved and
closed, a box pops up stating the following:

"Changes to the meeting cannot be saved. The meeting has been updated by
another person. Close and reopen the meeting, and then make your updates"

I found one reference to this so far and the fix has been to re-open Outlook
each time the error prompts which, I guess, is better than restarting the
computer .....