[Users] Proxy Authenticate error

This may not be an openser issue, but I have Netcomm NB9W UA which does not do Proxy Authentication. This is the setup: UA (202.74.186.77) => Openser proxy (202.74.164.44) => Registrar (202.74.164.72) The UA makes a REGISTER request which gets forwarded by the proxy to the registrar. The registrar then replies with 407 Proxy Authentication Required message which gets forwarded by the proxy back to the UA. The UA then seems to ignore this and re-sends an unauthenticated REGISTER reuqest. Attached is an ethereal dump showing this behaviour. My question is, is there something that the proxy or registrar are doing incorrectly which causes the UA the not do proxy authentication? I can't see anything. Thanks, Jeff