When you uninstalled and reinstalled did you use MCPR removal tool under Useful Links at the top of this page?
Could you try running MVT found under Technical Support and post the details the report will give you. This will help us to know more about the installation of your McAfee software such as version number, build date, etc.
Please post the session number here for a tech to reference and contact Technical Support for more help. They can remote connect into your computer to see if anything might be conflicting.
Have you done a system restore lately or installed any other software? Did you ever have any previous security software installed before McAfee?