Comment 3 for bug 201143

OK, I figured this one out finally, looks like under firefox 3 plugins a symlink is missing.

What worked for me:
alex-mayorga@inspiron-1501:/usr/lib/firefox-3.0b3/plugins$ sudo ln -s /usr/lib/jvm/java-6-sun/jre/plugin/i386/ns7/libjavaplugin_oji.so

Before:
alex-mayorga@inspiron-1501:/usr/lib/firefox-3.0b3/plugins$ ls -la
total 8
drwxr-xr-x 2 root root 4096 2008-01-02 17:09 .
drwxr-xr-x 5 root root 4096 2008-01-17 22:55 ..

After:
alex-mayorga@inspiron-1501:/usr/lib/firefox-3.0b3/plugins$ ls -la
total 12
drwxr-xr-x 2 root root 4096 2008-03-13 16:29 .
drwxr-xr-x 5 root root 4096 2008-01-17 22:55 ..
lrwxrwxrwx 1 root root 64 2008-03-13 16:29 libjavaplugin_oji.so -> /usr/lib/jvm/java-6-sun/jre/plugin/i386/ns7/libjavaplugin_oji.so

Looks like the Java plugin is not symlinked under Firefox 3.