<p>I have Java 1.5.0 installed on a Mac OS machine. I have the Java Embedding Plugin 0.9.6.4 installed and java enabled on the preferences panel. When I go to <a href="http://java.com/en/download/help/testvm.xml" rel="nofollow noreferrer">http://java.com/en/download/help/testvm.xml</a> the applet appears blank. Does anyone has an idea of what is happening?</p>

I have found the solution. The Java Embedding Plugin uses the installed JVM which itself gets its proxy definitions from MacOS and not from Firefox. So, proxy definitions have to be defined for both MacOS/Safari and Firefox.
I've also updated Firefox and selected Java 1.5 on the Java preferences panel. However I'm not sure if these two actions helped solve the issue.