ISA 2006 LIVE MESSENGER AND YAHOO WILL NOT WORK?

Hi all, We are having problems with Live Messenger and Yahoo do not work with separate ISA 2006, our configuration is to allow all users traffic out with no exception, as all our users is the Internet traffic through a proxy, if I omit proxy server and go straight through the firewall that works well (which is the policy for the IAS server) -. I turned on logging and get the following: 12209 The ISA Server requires authorization to fulfill the request. Access the Web proxy filter is denied. This is the port 80 is really strange. We are also using Skype through a proxy and a great job. Could someone give me some advice on what could be causing this? I found a lot of articles about how block, but nothing to make them work.

I think ISA server is administator Internet? "Anyway, if ur able to go the route, it seems u have to upgrade or update 2008-9 to live messenger, yahoo n 2008. NO-NO upgrade to Internet Explorer 8, 2 many problems, n is not compatible with several programs. i did, and got rid of it. the version Windows Live Messenger recent think it's great, live messenger similar to yahoo messenger. Like me, n keep. I really hope this helps. alos if u are looking to get a book on the (no offense) Internet for Dummies (again no offense), IDG says the book. should help. i, m reading my 3 rd.