If you have problems running BankID (Norwegian Internet bank authentication) in Firefox on Ubuntu I might have the solution. I did at least have some problems starting BankID or more correctly starting Java in Firefox on Ubuntu.
First, go the the plugins folder where you have installed Firefox (using a text shell/command prompt).
Next, create a symlink to where you have installed the Java plugin.
sudo ln -s /usr/lib/jvm/java-6-sun/jre/plugin/i386/ns7/libjavaplugin_oji.so
Finally, restart your browser and the problem should be solved.