I upgraded to the 3.6 package. Working well. As noted, Java plugin was not showing in about:plugins following upgrade. I went back to Gslapt, upgraded the jre package to 6U18, and did nothing else. Restarted Firefox, and about:plugins shows the Java plugin. I confirmed it was working on Java's browser test here: http://www.java.com/en/download/help/testvm.xml
So seems like an even simpler fix than johnvan initially described (in VL 6 standard, anyway)...much appreciate your pointing it out though, John - I likely wouldn't have noticed the plugin was missing until I really needed it, and then would have panicked and borked a whole bunch of who knows what trying to fix...