Check your Outlook version, if it is sandboxed and compliant with the new Mac OS X security features. See this thread, i.e. the post by Rishi Garrod:
This seems to be a problem with the sandboxing in Mt. Lion. I do not know of any work-around so far, sorry, until a compatible Outlook version will be available.
No, but it seems to be a similar situations as with Aperture and iPhoto plug-ins, see for example: