Good point - I know both of those hosting services don't play nicely with the occasional forum from time to time. However, while I'm not concerned enough about the lack of an avatar to be bothered signing up with ImageShack, I did try hosting it on my own website and linking directly from there. Same result... I'm guessing there's another factor in play here that we're unaware of, perhaps a hiccup in the IP.Board code, or something like that.
Of course, my own idiocy should not be ruled out