If you did not know Microsoft has been spending a lot of time tweaking Outlook 2007 to work better with large mailboxs as they push for 10GB mailboxes in Exchange.
If you have ever had a large mailbox in Outlook you have seen it hang or take a long tim to startup, or not close properly.
Outlook 2007 SP2 is intended to fix many of these issues but has not been released yet, but luckily Microsoft saw the benefits and has released a hotfix that you can download ( http://support.microsoft.com/?kbid=961752 ) and start experiencing the performance enhancements for Outlook 2007
I must say I just installed this, so I don’t have any feedback at this time but I would recommend you installing the fix.
For a list of the changes reference the following article http://support.microsoft.com/?kbid=968009