java SecurityException when running applet on firefox, ubuntu

Question

I would like to run an applet on firefox 3.6 on ubuntu 10.4. and I start firefox with sudo on command line to see the java console output. My appplet code changes some policies and it works fine on windows. But on ubuntu I get this error:

java.lang.SecurityException: Changing the SecurityManager is not allowed.
    at net.sourceforge.jnlp.runtime.JNLPSecurityManager.checkPermission(JNLPSecurityManager.java:267)
    at java.security.Policy.setPolicy(Policy.java:256)

Is there a way to get around this problem? I saw on some other thread that adding -nosecurity on javaws helps. But I don't know how I can apply something like this on firefox.

Thank you very much