Empty Allowed List in Windows Defender

I use Windows Defender in a Vista Business environment.
The application seems to work well, warning me every now and then when it
encounters new applications or changes in my startup. Updates are done
frequently too. I also join Microsoft Spynet as basic user.

However, when I ask for a list of allowed items, this list is empty
(although I approved many items). How can I invoke this list??

Many Thanks for your advice and help.
--
Joey Dalton