I have a problem joining the Happydiggers TFC server (both regular and hardcore). When I attempt to login in, I receive the error "Failed to connect to server; Error occurred while contacting login servers, are they down?". http://xpaw.ru/mcstatus/ confirms that the login servers are not down.
I can connect to at least one other TFC server, and according to dynmap nobody is logged in at the time of this post. So it seems at least plausible that the error is on the server's end rather than mine.