When did you first install McAfee?
Was it purchased online or a retail store?
Did you previously have any security software installed prior to installing McAfee?
Did your computer have any prior malware or virus infections?
Try running the stinger which is mentioned in the document and see if it finds anything.
You could also try to run the McAfee Virtual Technician which is found at the top of this page under Useful Links in the Technical Support area. MVT will scan your computer for any McAfee related issues and if it finds any it will attempt to fix them.
You could also try this program if you still can't install any updates to see if it might find something. http://www.malwarebytes.org/mbam.php Download the free version and install the program and check for latest updates. It might be to your benefit to download this on a usb stick before attempting to install on your computer. If you can get it installed run the program and let it clean everything it finds and reboot the computer if prompted to do so.
Also why 2009 you should consider updating via your account to 2010 version