Well, if you aren't using internet explorer that could be the problem. I'm not sure what the problem with using firefox is but I know the MHF client wont load if you use firfox without a special add on. I just use internet explorer myself.
If that isn't the problem check the bottom left corner of the IE window and if it says something like "There is a Error on this page." than thats your problem. This happened to me once or twice but every time I just reboot and its back to normal. Hope I was helpful.
