This happens to me both on my laptop and my desktop ALL THE TIME. It's been going on before the forum wipe too (on old forums) for months. I clear cookies or cache and it works momentarily and then goes back to doing it all over again...annoying.
I'm not really sure. I use our forums on 5 different computer over the course of a typical day and none of them have problems with our website or chat. It really falls into an area of if I can't see it, I can't fix it.