I have been with cox years and had the same issue , it is cox website and it has nothing to do with your computer .
You need to contact cox support ask them to come fix the problems you have beside nothing is going to take place because the wiring for cox is so old and like on my street most of time I have no connection at all and they keep telling me they are in process of fixing the problems and I have confirm this with some of my street people whom are living near me and they are complaining about the same issure .
I think give them a call and see if they are willing to help out otherwise there are other companies around at lower cost and less headach .
I have my office out of this area and have been with att for years never had a problems in years , I mean in years but at home where I have cox always slow and always problems.
thanks