the same thing has been happening to me for a couple days now, in Chrome. I just type "www.comcast.net" in automatically, realizing it redirects to something else. Will try to start using "xfinity.comcast.net" instead, since that's actually the site at which I need to be.
What's weird is that it always redirected just fine, even in Chrome, it's only just recently that I ever saw the ominous "this is probably not the site you are looking for!" message about a248.e.akamai.net.