Quite an annoying message when you're trying to connect to an irc channel to get some help. You stay connected for a while, and then get kicked off the channel with the message above.
When I'm in a real, real hurry and have no wish to try resolve the issue, I just go to the web-based IRC client - http://mibbit.com/ and connect to the channel I need. It works fine, I get the help I need.
Could not resolve your hostname: Domain name not found; using your IP address instead - still don't know for sure how to bypass this. Also because in some clients like Konversation or XChat the error doesn't prevent from using the channel, while in others it results in getting disconnected.