Do you have this same problem with say, watching netflix or hulu or is it just ESO?
Off the top of my head, a couple of potential causes would be an IP address conflict or a virus. (Viruses are kind of a catch all. They can cause all kinds of symptoms.)
Gorecleave wrote: »Try using a wired connection to your modem if you aren't already. Not sure what you meant by "cable wifi". What model router do you have?