This is probably not a problem with your McAfee AV software. It's a recent issue connected with Google and Facebook, and they're talking about it over on the Google forums (which are well worth keeping an eye on).
If you go on over to one or two of the discussions you might find someone has a bit more information than we can probably offer for this. Try
There's also an old discussion at
which might be useful.
Good luck with solving the problem, the Google forum's your best bet for this.