That's strange considering McAfee and Facebook are partners.
Exactly what components do you have installed?
If you have the square taskbar icon then it's the 2009 version - open SecurityCenter by double-clicking it or right-clicking it
Click About in the lower right corner and it will tell you the versions of each component. Please post that information.
If you have a shield-shaped taskbar icon then it's the 2010 version - open SecurityCenter by double-clicking it or right-clicking it
Click Navigation in the upper right corner, then About at the left and it will tell you the versions of each component. Please post that information.
Security Center - Version 9.15
Virus Scan - 13.15
Personal Firewall - 10.15
Site Advisor - 3.0
Anti-Spam - 10.15
Parental Controls - 11.15
Let me know if you need additional info.
Is IE8 totally up to date along with add-ons such as Adobe Flash and Shockwave and Java? For that matter is Windows 7 totally up to date?
It puzzles me because I've had no issues with FB at all.
All I can suggest at present is to go to IE8 Tools/Internet Options/Advanced and click Reset, Apply and OK it.
Close and reopen IE8 and then go to Tools/Manage Add-Ons and re-enable the add-ons.
Try it again.
Try the Firefox browser opening Facebook once you have McAfree installed. I have the same set up and it's not a problem. Any version of IE is inferior to Firefox in my opinion