You configure Microsoft Live Meeting 2007 by using automatic configuration where only the A records are configured and not the Service Location (SRV) records. In this situation, the test connection process fails. Therefore, you cannot join conference calls by using the Live Meeting 2007 console.
This issue occurs because the test connection uses TCP, but not Transport Layer Security (TLS). The front-end server listens to port 5061 by using the TLS option. Therefore, the test connection fails.
To fix this problem, install the following cumulative update:
2433231 Description of the update package for the Windows-based Live Meeting 2007 client: November 2010
To work around this issue, apply the following methods:
Configure Live Meeting 2007 by using SRV records instead of A records.
Configure Live Meeting 2007 by using advanced settings and specify the server name, port and protocol.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.