Could be either of a few problems, main one would be your service provider, at peak times it can be slow so check your net speed, (least you know if your slow or not then)
Try clearing the forum cookies from your explorer options.
could be your browser its self, try downloading google chrome, or firefox. (ie 8 is pretty crap in comparison)
it could be the forum its self maybe its very busy with users, its bandwidth limit is drawing close or the server needs resetting.
try the first 3 see if they improve your service.