Citrix have a private hotfix to address issues with the Access Gateway 4.2.3 experiencing a hang when changes are made to a Logon Point in Advanced Access Control. If you are experiencing the issue, give the good looking guys at Citrix Support a call. You will have to give them information about your setup and they should be able to give you the hotfix to test out. If you are experiencing the issue, why not share your experiences over at the Brian Madden forums.