LAN not connecting above local only

Hi All,

At my school, we have a self configurations system that works on the LAN as the campus it too large to have Wireless, So what is meant to happen is that you plug in the Ethernet cable with No Configuration. Then you attempt to go to an internet site and you are automatically redirected to this site where you have to type in you School user name and pw. Then you download this program called bradford dissolver which detects whether or not you have any form of mainstream antivirus such as norton, mcafee, AVg or avast or some other brand unknown to me, but it doesn't block the antivirus servers so you can update the antivirus. However, I have Avast and updated it and then it asked me to restart and since then I have not been able to get to the page which it redirects you to. any ideas, the tech support here is useless that i why i haven't bothered asking them