Are you by chance running Internet Security Suite 9 ?
McAfee released an upgrade at the end of July. It has been a complete disaster. They have issued several patches, all which have had limited success.
Have you gone to?
http://forums.mcafeehelp.com/viewforum.php?f=103&topicdays=0&start=780 The forum makes for an interesting read. Often there is no mercy given to those techs. (Especially after the 1st patch)
One of the many known issues is that it is NOT compatible with much software.
There are temporary workarounds on the forum. And I noticed another new patch was just been released.
Funny thing is, it works fine on some computers and wreaks havoc on others. We are experiencing problems on only one computer. Most folks on the forum are complaining that IE and AOL is slow, and that specific software does not work .
I do not know whether are not they are having problems with the other suites. I do know this one rendered our computer useless for several days. I have used McAfee for years, and it is not until now that I have considered changing.