Today I started getting a fabulous new message from Outlook 2007 whenever I tried to open pretty much any type of object, i.e. a mail message or a calendar appointment: Could not install the custom actions. The object could not be found. Curious I thought, this was all working yesterday. It turns out it seems to be a corruption of the form cache file frmcache.dat . Close Outlook. Wait a few seconds for it to finish shutting down in the background. Go to your c:\users\[ USERNAME ]\ Appdata \Local\Microsoft\FORMS directory and delete the cache file from there. Restart Outlook and the problem should have gone away.