so it turns out there was a thing somewhere which still referred to the old server so some but not all people would be redirected to that machine for name lookups for, say, "kintsugi.seebs.net", and this is now probably fixed mostly but may not be fixed for everything.
long story short: there can be as much as a two day lag before something somewhere in the system wipes out its cache. the problem is that some things think they need to ask the old server to look things up. unfortunately, there's nothing we can do to tell them they're wrong except wait. rebooting routers and the like might help.