Microsoft has identified several issues with a recent Outlook updated (KB2412171).
If you are experiencing one of the following issues, you might be affected:
- Slow performance while switching between Outlook folders.
- Missing AutoArchive functionality.
- Issues with password authentication while sending or receiving email.
Microsoft recommends uninstalling update KB2412171 if you experience any of the above symptoms. Only Outlook 2007 is affected. You can find more details in this article. Microsoft also published KB2485531 on this issue.
Update: On January 11 2011, Microsoft issued an update which is supposed to fix the three issues listed above.