See this thread:
[SOLVED] Outlook 2007 Crashes After Installing the Connector
The comment on 4/2/09 at 9:15 states:
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It turns out that the solution was something simple. When you install Groupwise, Windows NT Messaging is also installed. After uninstalling this and then reinstalling the connector, everything works fine.
It was not necessary to replace mapi32.dll, reinstall Office, or do any registry hacking on the XP machines we were able to fix. However, in Vista, you have to do an Office repair or uninstall and then reinstall Outlook after uninstalling Windows NT Messaging. Also, on one of the Vista machines, we had to run FixMapi before we could successfully uninstall and reinstall the connector.
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Hope this helps.