Office Communicator Certificate Error

have just installed Office Communications Server 2007 R2 on Server 2008.

I created a self signed certification on the server running OCS. At this point web access works just fine. However when I try to connect using Office Communicator , the following event is registered and the connection fails.

The server I generated the certificate on, and the PC I am connecting from, are all part of the same domain. Not sure what to do at this point, and my certificate experience is limited. Given the number of users, I can't manually install a certificate at each workstation.

Error event:
Event Type: Error
Event Source: Communicator
Event Category: None
Event ID: 5
Date:  10/18/2009
Time:  1:45:32 PM
User:  N/A
Computer: 1175PC
Description:
Communicator could not connect securely to server ocsserver.companydomain.local because the certificate presented by the server was not trusted due to validation error 0x80090325.  The issuing certificate authority (CA) for the server's certificate may not be locally trusted by the client, the certificate may be revoked, or the certificate may have expired.