Limted/no Browsing With Internet Connection Windows 7 Upgrade

I am running Windows 7 Upgrade on a Dell Inspiron desktop. As of Thursday, June 16 after Windows Update and McAfee Update, I have had difficulty browsing the internet, alhtough I have internet connection. After hours of phone conversation with Dell and my IP, hours more of online chat, I am still not satisified anything has been corrected. I am currently connected to the internet through problem computer. Wired, DSL. I replaced phone and ethernet cable. Dell support basically useless as they want big bucks to fix problem and I can barely understand them. My IP spent 6.5 remotely accessing computer, eventually giving up, claiming that they had met their match. I have done two clean installs, but after Windows update, the problem returns. I clean installed a third time this afternoon. Downloaded MSE, updated and that went without incident. I have been browsing and researching this issue at many sites and forums, this evening. I hesitate to update Windows further, as I have finally returnd successfully to the internet. McAfee is not currently installed. I have of intention of installing it. I'll give MSE a try. Can anyone provide possible answers to what is causing the conflict (if that is what it can be called) with browsing after Window 7 update? The modem disconnected occasionally, but according to my IP is working properly. Computer appears to operate fine otherwise, just the browsing.