Outlook 2002 accessing Exchange 2003 SP2

When one of my users tries to accept or view a meeting invite from a
particualr user, they receive the following...

"You changed one of the occurrences of this item, and this instance no
longer exists.  Close any open items and try again."

Appears that this has started after applying KB946985 (Security Update for
Outlook 2002 patch).  Short of uninxstalling this patch, what could be
causing this situation?

Is anyone else seeing this behavior?

Thanks!