Have you been using registry cleaners and/or optimizers? They will do this to you all the time.
The business between IE8 and McAfee was ages ago and only referred to IE8 beta, no problems at all with IE8 now.
IE set at default settings has no problems.
Is Windows totally up to date? What version and service pack?
Also what version of McAfee is installed - does it look like this?
Have you checked for malware?