http://blogs.technet.com/daveh/archive/2009/03/30/error-joining-im-livemeeting-conferences-in-office-communications-server-2007.aspxYou may find that all users within an OCS Pool are unable to join a three-way IM conference or join a Live Meeting conference in Office Communications Server 2007.  In examining the logs of the OCS 2007 Front End server, you may see the followingen-USCommunityServer 2.1 SP1 (Build: 61025.2)