When this happens it is usually caused by an Add-In. You can disable them to resolve the problem.
First, open Outlook in Safe mode. Close Outlook. Click Start and in the Run box type Outlook /safe, (there is a space between Outlook and /). Once it opens, click File, then Options. Click Add-Ins. Then in the Manage section toward the bottom, make sure COM add-ins is chosen and click Go. Un-check all the Add-Ins and then click OK. Restart Outlook normally.