If you recently downloaded an update for Outlook 2007 and find that toggling between folders is very slow, and your computer is locking up - here is the link to uninstall the update.  Microsoft is aware of the problem and has issued uninstall instructions.  I literally added two hours to my day yesterday because of this problem.  Glad i found the answer!!
http://blogs.msdn.com/b/outlook/archive/2010/12/17/issues-with-the-recent-update-for-outlook-2007.aspx