A friend of mine tries to join us on a free TeamSpeak server without password.

TS has firewall and antivirus permissions.
He can actually log into the server, but after a few variable seconds, without being able to talk, he gets timed out. Always.

We've reinstalled TeamSpeak, run the setup wizard, all voice test ok, but then he keeps getting time outs. He gets time outs on all other server's we've tried, but not in other live-voice programs, such as Skype.

Can anyone offer a solution?

Thanks in advance.