Scott Oseychik over on the MSDN blogs has a good post today about federation issues between OCS 2005/2007 and AOL. Apparently, American Online changed their root certificates on their SIP Access Gateway at approximately 12/2/2008, 4:00 AM EST.Via Scott's post:
If your organization leverages Public Internet Connectivity (aka: "PIC") in conjunction with their Live Communication Server 2005 and/or Office Communications Server 2007 servers, you may not be able to successfully communicate with (or see the presence status of) America Online Instant Messenger users.
Read more (including a video walkthrough on how to resolve the issue)
