Click start > Run type in inetcpl.cpl
Next go to the advanced tab and locate "Enable third party browser extentions" uncheck this. Apply the setting. Next go into the programs tab and click manage addons.
Look for any number/letter entry or entries that do not have a publisher and disable them. Spybot S&D will have one.(This can be left alone) Next close out of all instances of the internet. The next thing to do is clear out your hosts file
c:\winnt\system32\drivers\etc\hosts
or c:\windows\system32\drivers\etc\
You can either edit this and delete entries found there or delete the file called hosts.
You can also do a search for hosts and delete the files that are just plain hosts you don't need to remove the lmhost files.
Next you should be able to browse and navigate as usual.
Hope this helps.
McAfee is great when it comes to anti-virus. But you still do need an anti-spyware program just to be safe.
Good luck