Try running the McAfee Virtual Technician found at the top of this page under Useful Links under Technical Support. MVT will check for McAfee related issues and will attempt to fix any found.
You could also try to uniinstall your software and reboot the computer. Run the MCPR tool and reboot again. Login to your online McAfee account and download and install your software. MCPR also found under Useful Links.
Let us know if these steps resolve your issue.
Is this the scan that happens during the early stages of the software installation? If so uninstall everything via Control Panel/Programs/Uninstall a Program (Add or Remove Programs in XP) then run the MCPR cleanup tool listed under Useful Links at the top of this page, reboot and reinstall.
It is either stuck or has found something it can't clean...have you had any other warnings?
Make sure that your system, whatever it is, is totally up to date in all aspects