I found the ultimate solution nobody yet found.
In fact, I had this problem and tried with several IRC clients. None worked. So probably it was a XP problem.
And definitely it was.
So it's a Winsock problem. Save your IP configuration for Internet. Then you will need to repair/reset Winsock configuration.
To perform this, download Winsock XP Fix 1.2 (at
http://www.softpedia.com/public/cat/13/9/13-9-161.shtml)Run it. Then you will reboot your computer. Configure your IP properties (since it's been cleaned) and the problem should be gone!!!!
Mav90