Aha - a little more digging explains it all: the glue is misconfigured. bdsmlibrary.com is configured with 'glue' identifying ns13.guihosting.com. as being 208.53.180.146 and ns14.guihosting.com. as 208.53.180.147 - but according to guihosting.com, neither of those servers exist at all!

This is bad, it IS a misconfiguration of the DNS hosting for the site, and it will cause problems (most obviously, anyone who has tried to communicate with the non-existent ns13 and ns14 will cache the fact that neither exists for several minutes, probably rendering bdsmlibrary.com unreachable) - however you look at it, though, it shouldn't be set up that way!