Sometimes messages come through like that when the problem actually resides in the browser system (Internet explorer, firefox, etc.). And that "problem" may be nothing more than an update(Windows typically does auto updates on Wednesdays) for which the virus protection hasn't yet updated, so a conflict sets up.
I'd try doing a manual update on your virus protection. Also, go ahead and do a manual update on your Windows, just to be sure. That'll probably take care of it.
Of course, as someone said above, never have two virus protections installed and active at the same time. They simply do not play well together.
Hope this helps.