Are you using IE9 beta by any chance? It isn't supported, see: https://community.mcafee.com/docs/DOC-1779
Also if you are not using that and regardless of which is your default browser, make sure that IE is the latest version, - 8, and go to Tools/Internet Options/Advanced. Click Reset, Apply and OK then cloae and reopen IE.
Go to Tools/Manage Add-ons and re-enable any add-ons you need.
That should fix it.
If none of that helps please provide more information such as your operating system and service pack. Also what McAfee products are you using?
If the taskbar icon is square it's 2009 version, double-click it to open SecurityCenter and click About and post those details.
If the taskbar icon is shield-shaped that's 2010/11 version and double-click to open SecurityCenter then click Navigation, then About, post that information.