Did you at any stage have IE8 Beta installed? We usually only see this with that particular browser version, whether it is the default browser or not.
Have you tried uninstalling/reinstalling?
If you are using IE6 then you must have XP, is it up to date? I also recommend that you upgrade to IE7 as it is safer.
Go to Control Panel/Add or Remove and look for McAfee Siteadvisor and uninstall it. If you have other McAfee products then it may be listed as part of McAfee Security Center. Click that item then select only SiteAdvisor for removal when the menu shows.
Reboot and then go to either your account online or http://www.siteadvisor.com
to download a new copy.