Sounds like it
could be a firewall issue, TSL. If possible, try disabling all firewall software for a minute and try then.
From mIRC's 'IRC Intro and Faq':
(23) Can our Firewall or Proxy be blocking my IRC session?
Yup, that is very well possible.... But most IRC clients support firewalls properly and you might simply have to adjust some options to get it working. You need a SOCKS 4 or 5 compliant IRC client to be able to IRC over a firewall. In some situations it is possible to connect to IRC through a HTTP Proxy. mIRC has a special 'Proxy' setting to accomody this. Ask your internet provider or corporate network managers if you are behind a firewall of some sort, and if so, if using mIRC will allow you to use IRC. (Read more on proxies and firewalls on
http://www.mirc.co.uk/help/proxies.html)