It looks like the SnagIt add-in for Outlook doesn't play nicely with Outlook 2007 -- I was having constant crashes when trying to open Calendar entries. That stinks. Acrobat 6 may also cause problems.
Unfortunately, it appears that Microsoft has left add-in management out of Outlook 2007. The only way to disable misbehaving add-ins is hack the registry. Open RegEdit and browse to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Outlook\Addins\SnagItOfficeAddin.Connect. Set the LoadBehavior key value to 0.
Things seem to be behaving a bit more nicely now.
(Hat tip: Slipstick.com.)