Symptom:

UserA in CompanyA (uses OCS) tries to join a Live meeting (using Live Meeting Console) organized by UserB in CompanyB (uses OCS).
CompanyA and CompanyB are not federated.

UserA cannot join the Live Meeting, when the UserAccount is configured in Live Meeting console.

UserA needs to delete the UserAccount and any external servers, to be able to join the meeting..

Cause:

Live Meeting Console, current expects that the CompanyB has the following SRV record deployed:  sip._tls.<CompanyB Domain>. This was not the case, and hence the join failed.

Resolution:

Request CompanyB to deploy the following the SRV record: sip._tls.<CompanyB Domain>. We are working on reverting to A records correctly, in case SRV records are not deployed. Look for a fix tentatively end of May'2011, as part of Cumulative update for Live Meeting Console.