Lync Server 2010, Response Group Service has declined the call. Request coming from '%1' was declined because a Ms-Application-Aor ...

Lync Server 2010, Response Group Service has declined the call.

Request coming from '%1' was declined because a Ms-Application-Aor header was not found in the set of headers the client sent to us.
Cause: There could be an error on the Front End server, or an unsupported/invalid client tried to connect.
Resolution:
Check for eventual SIP errors on the Front End servers and the versions of the clients.