MVP Susan Bradley has posted the following. See if it fixes your issue:
A number of users are reporting performance issues with Outlook 2007
after installing update 2412171. Possible symptoms include:
* Slow performance when changing folders, especially folders that
are in different message stores.
* Loss of Archive functionality
* Errors receiving mail on accounts that use Secure Password
Authentication (SPA)
*How Do I Fix it?*
At this time the only fix for it is to uninstall update 2412171, which
you can do in one of two ways:
1. Control Panel> Add/Remove Programs. In Windows 7 click "View
Installed Updates", find KB2412171 and uninstall it. In earlier
versions just make sure the "Show Updates" checkbox is checked and find
the update on the list. This is the best way to do it, as a general rule.
