McAfee Security Scan Plus can be removed from your Control Panel/Programs and Features/Restart. Please do that, and see if the Warnings disappear. As this program is basically a 'Marketing Tool' It checks your system for Anti-Virus software, and has no protective values at all.
Also,occasionally when you open Internet Explorer, it will show dialogue at the bottom of the page, suggesting to disable add-ons.
I recommend that you keep your McAfee Web Advisor enabled/Active, as it has layered levels of protections while you surf the web.
I hope this helps...
Sometimes it is inadvertently downloaded/Installed with Adobe Products.