Error Message at OCS Mediation Server "The A/V authentication service cannot be contacted"

I have got following error message when i started mediation Server services:

"The A/V authentication service cannot be contacted. Connections that require firewall traversal will not be succesful"

For resolution, i checked all standart says, e.g communication port (5062), internal names of Edge and Front-End, but no any problem for that, like everything is ok! But source of problem is certificates on both edge servers and mediation server. I changed all name in certificates as including all external names and all internal names. And problem solved after restarted edge and mediation server services.
More: http://www.mshowto.org/