or those that subscribe to the Public Internet Connector (PIC) feature in Office Communication Server, a recent change at AOL may impact you. As with all communication to and from OCS, certificates are used to encrypt and authenticate traffic. The PKI infrastructure AOL utilized in the past has changed and they have moved to their new AOL root certificates. Because of this, the OCS Edge/Access Proxy servers will not be able to validate any AOL traffic without a root certificate update.
The official notice may be found here:http://blogs.msdn.com/scottos/archive/2008/12/02/office-communicator-clients-cannot-communicate-with-contacts-homed-on-aol.aspx
A link to the AOL certificates may be found directly here: https://pki-info.aol.com/AOL/
Remember. only the edge servers (those authenticating traffic) require the updates - not your clients - and a restart/reboot is not required