AOL has change there Root Certificate.
You can download them at https://pki-info.aol.com/AOL/

These 2 need to be imported in all Office Communication Server T – rusted Root Certification Authorities

You can see a video on howto import these 2 certificates here: http://simsbury.members.winisp.net/Update-AOL-Root-CA.wmv

There errors is belov

Multiple invalid incoming certificates.

In the past 1185 minutes the server received 12 invalid incoming certificates. The last one was from host 64.12.162.248.
Cause: This can happen if a remote server presents an invalid certificate due to an incorrect configuration or an attacker.
Resolution:
No action needed unless the number of failures is large. Contact the administrator of the host sending the invalid certificate and resolve this problem.

Over the past 0 minutes Office Communications Server has experienced TLS outgoing connection failures 1 time(s). The error code of the last failure is 0x80090325 (The certificate chain was issued by an authority that is not trusted.) while trying to connect to the host “sip.oscar.aol.com”.

Cause: Wrong principal error could happen if the peer presents a certificate whose subject name does not match the peer name. Certificate root not trusted error could happen if the peer certificate was issued by remote CA that is not trusted by the local machine.

In the past 0 minutes the server received 1 invalid incoming certificates. The last one was from host 64.12.162.248.

Cause: This can happen if a remote server presents an invalid certificate due to an incorrect configuration or an attacker.