From the Kazaa help file.
What Internet Providers might block Kazaa?
Possible Internet Providers blocking KaZaA:
AOL
Road Runner
Charter Communications
AT&T
Some Internet Providers block port 1214 which is key in making Kazaa Lite work. Some Internet providers don't block the port, but find other ways of blocking Kazaa (Lite) and other p2p applications. Read below on how to see if your port 1214 is blocked.
How can I see if port 1214 is blocked?
You can check this with a local port scanner. Make sure KaZaA Lite is running when you do the scan.
What can I do if port 1214 is blocked?
Usually when port 1214 is blocked, this is because of a firewall or a proxy server. With programs such as Socks2http or Http-Tunnel you can bypass these firewalls and proxies.
If you use Kazaa Lite 2.0.0 or higher there is another thing you can try:
Go to Kazaa Lite options. Go to the firewall tab. Change the port from 1214 to anything above 5000. For example use port 7000. This way you don't have to use any of the tunneling programs described above. Just as you have no restrictions. Now the first time you connect with this new port settings may take some time. As soon as you are connected for the first time, the next times it will connect much faster. If this trick does not work, then try some more ports. You can also try ports such as 21 and 80.