If you have not installed Office 12.1.5, I suggest not installing the Mac OS X 10.5.6 at the same time. Not that I expect problems, but if you do experience a problem, it’s easier to troubleshoot one update at a time.
I installed Office 12.1.5 on December 9 when it was released then OS X 10.5.6 on December 15. I’m seeing no conflicts using Entourage 12.1.5 with Leopard 10.5.6.
Suggestions for a good update.
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Continue Reading: Office 12.1.5 and Apple 10.5.6 updates