Hi, I'm runnig Squid 3.0.STABLE19 , using plain proxy auth (auth_param basic program /usr/sbin/pam_auth). Some time ago , I had troubles when trying to login to Windows Live Messenger. It began to causing problems when i enable the proxy auth. I could not make it work. My solution was installing Pidgin http://pidgin.im/ . In Microsoft's page http://support.microsoft.com/?scid=kb%3Ben-us%3B927847&x=1&y=8 , quote : Users behind some authenticating proxy servers may experience sign-in issues. They might have to configure the proxy servers to force authentication for the following User Agent string: MSN Explorer/9.0 (MSN 8.0; TmstmpExt). To do this, users should see the documentation for their proxy server or contact their network administrator. Is this the fix for this issue? How can i implement it? Thanks!