I do a lot of work these days in Java and recently I wanted to be able to test a web application that uses Java Applets from my Ubuntu Karmic client. When loading the first applet and viewing the Applet Console window I noticed Firefox would hang and the last line in the console was:
network: Firewall authentication: site= protocol=http, prompt=, scheme=ntlm
It seems there is a bug in the JDK version for Linux (and MAC OSX) when it comes to NTLM. If you have access to the webserver that serves the web application and it happens to be IIS, remove Integrated Windows Authentication and viola… Linux works with your applets.