I’ve recently been having problems with Microsoft Office 2007, and Outlook specifically, running very slowly. Outlook would frequently become non responsive and take several long minutes to regain control. After some digging around I’ve found that the best solution has been to disable any unused plugins. After removing several (SugarCRM, GTD) Outlook has now once again become usable, albeit not a speed demon by any measure.
For more information see the following: http://pastorrod.blogspot.com/2007/03/why-is-office-2007-slow.html