In Microsoft Office, there is an OST Integrity Check Tool (Outlook 2003 & Outlook 2007), but there is no easy shortcut. I recommend making a new shortcut for your Start Menu group like this: "C:\Program Files\Microsoft Office\Office12\SCANOST.EXE"
UPDATE: If you're having frequent problems, a couple files in %APPDATA%\Microsoft\Outlook may be corrupted: outcmd.dat & Outlook.nk2. While Outlook isn't running, rename those files.
Also, disable unused add-ons easily with OfficeIns.
