Trusted sites in IE7 (Windows XP) are not active - how to activate?

Greetings!

I have several Windows XP SP3 computers that will not allow additions to be made to the Trusted Sites inside IE7. I click on the Sites button & all the options/controls are greyed-out. How do I make this active again?

Thanks in advance.

Mike

Check if this MS KB might apply You cannot add a Web site to the "Trusted sites" zone when Internet Explorer 7 is installed even when the user account belongs to the Administrators group

Note a bit under the title on the MS page, they provide a link to View and request hotfix downloads. Click on it to get their hotfix

Update: I tried the hotfix, but it didn't help. I'll keep searching for now. If I find something that works, I'll post it here.

Thanks for the suggestion, though!

Mike