Meh, slow loading's happened to me a few times. At one point, ZU wouldn't even come up; rather, an error appeared in its place saying it couldn't find the address, please check your spelling (though I'm using the same bookmark I've been using for over a year now) et cetera, et cetera. All other sites are fine when this happens. Personally, I think an aversion (whether it's my computer's or connection's, I'm not sure) to ZU is the cause. Most likely not widespread.