Windows 2000 does not have a software firewall by default like XP does. Most likely the problem is your wireless device. Most wireless devices have internal NAT firewalls which is why it is imperative we know those details.

It may even be worth downgading your java. But more about that later after we get more details. Some people have problems with java 1.6 & downgrading to the 2nd last java 1.5 release often fixes their problem.