This error can occur if no program is properly set as the default for links. Sometimes it will happen after a browser such as Firefox or Chrome are installed. Check the Default Programs and try setting Internet Explorer as the default for all of its associated file types:

1. Open the Control Panel
2. Open Default Programs (you may have to click on the Programs group depending on your view settings).
3. Click "Set your default programs"
4. Click on Internet Explorer in the Programs list.
5. Click "Set this program as default"
6. Click OK

Try your links in Outlook. If it works after this change, then you should be able to go back in and change the default to whichever browser you want.

Hope this helps.

-SW