Hi there!!!
Try deleting the plugin first:
Code:
rm /usr/lib/mozilla-1.4.2/plugins/libjavaplugin_oji.so
then make a new link:
Code:
ln -s /usr/java/j2re1.4.2_04/plugin/i386/ns610-gcc32/libjavaplugin_oji.so /usr/lib/mozilla-1.4.2/plugins
see if that helps. If not, then make the link to your /home/user/.mozilla/plugins and see if that helps. If not, try linking other plugins, as ns610 instead of ns610-gcc32. It it still does not help, download a new JRE, it get broken all the time, specially the j2sdk

.
Side note though, you've to be root to perform those operations, and apperently, you are not:
Good luck!