Connectivity Issue

All was well until a few days ago when I gave in to the nag screens and let Avast 7.0.1456 install. Almost immediately I started to have problems which are detailed here in the last couple pages:  http://en.community.dell.com/support-forums/virus-spyware/f/3522/t/19438120.aspx  And it never did finish installing.

With the help of the forum members there we are working on getting the issues of firewalls and antivirus programs resolved, including having the Windows Firewall stay on, upon startup.

Somewhere while all this going on, I started to have problems getting connected to MSN.com, my homepage and portal I guess you could call it. Many restarts and couple of System Restore's were in the mix, so what I have apparently done is corrupt some settings. The strange thing is, is that there have been times the last few days where MSN did come up and I could get into my Hotmail account, but then when I went to another site, like Dell.com,  I would get the error message that Internet Explorer could not access that web page, and then it would not go back to MSN. And then, just awhile ago, I could not get my security programs to connect, even though they don't go though Internet Explorer, like MSN and all my Favorites do.

I don't think is any real connectivity problem, because the computer I am using now is connected to the same modem. I have tried to unplug and replug the Ethernet cable to the problem computer, but it didn't seem to have any effect. The computer is an XPS 420 running Vista. Any ideas on how to start resolving this problem very much appreciated. Hopefully this is in the right forum.