Are you using SSL to connect to any of the servers?
Try turning remote off (type /remote off in any mIRC's editbox and reboot mIRC) and see if it still occur.
If turning remote off doesn't do it, try reinstalling mIRC using the following steps:
1) Run the mIRC v7.43 installer
2) Choose an mIRC install folder in your Documents folder.
3) Check the "portable" option in the installer.
4) Install mIRC.
If it still happen on this new install, type in any mIRC's editbox:
//echo -a $os $version $file($mircexe).sig $alias(0) $script(0) $dll(0) $com(0)
and report the result here please.
Kiwi irc is a web application, meaning your connection is not used to make the connection to the IRC server.
If you have an Antivirus software, try shutting it down during your test, same for firewall from your router/Windows