I've the JDK 1.4.0 (as well as the jre) properly installed on my computer. When I installed a fresh copy of 1.0RC1, it doesn't find the plugin automatically. I've to manually copy the NP* files from the JRE directory. ouch.
dupe of plugin.do_JRE_Plugin_Scan do not support version 1.4 *** This bug has been marked as a duplicate of 134631 ***
or perhaps bug 133752
or even 100393, a duplicate for sure