http://blogs.technet.com/b/lync/archive/2008/01/08/unable-to-do-a-three-party-im-conference-in-office-communicator-2007.aspxTo take a look at this issue, we created the following test scenario. We setup an Enterprise Consolidated Configuration with two Front-end servers in the Pool with an F5 load balancer that also had two Standard Edition Servers in a Director Array withen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)