I believe this is an Outlook's mechanism in action when a situation of save conflicts is detected (just like in Lotus Notes). It's something like when you are trying to save a modified item and then the program performs a check to see if the back-end copy's content has any difference before and after the current user has modified and generates that message when it detects a conflict after the content comparison.

I can now appreciate why for Domino BES, they have to create a separate BlackBerry State database instead of writing the RefID into the mail document itself... to prevent events of "Save/Replication Conflicts".