Just thought I’d bring up something. Although not a definitive answer, it appears the reason you can’t connect to some servers is that their servers IRCd kills the client cause of it’s ident (how the server recognizes you).
Right now, the server I help operate is installing a new IRCd with a fix to allow DreamPassport chatters on. This is because many of the Brazilians who also chat at this server have been trying to connect… and failing.