The new version of mIRC asks Windows to return both IPv4 and IPv6 addresses for a domain name. It could be that for some users resolving IPv6 is slower than for other users for some reason. It is possible that the delay could be due to an ISPs name servers or your Windows configuration. I will change the DNS lookup in the next version so that it only asks for IPv6 if you have explicitly requested it by using/enabling features that need it.