There are 2 possibilities either some new proxies or that Optus may be
having some Nameserver issues.

Those that are having trouble connecting, you may want to alter your
/etc/hosts file. replace the line:
131.244.9.101 minnie minnie.tuhs.org

with:

65.49.60.197 www.oztivo.net

Also change your /etc/oztivo.conf file so that the emulatorport= line says
emulatorport=9090 (if it doesn't already)

Reboot and then try a call again.

Peter.