Trusted Sites for IE 8

I have a 2008 R2 domain with XP clients. I have defined trusted sites for IE under GPO. Now the IE 6.0 clients can edit trusted sites but on IE 8.0 clients can not edit the trusted sites.

I have also tried the workaround from the following link which is also not wokring.

http://social.technet.microsoft.com/wiki/contents/articles/4469.aspx