Update Aug 16, 2011: The latest Firefox is not working with JDK plugin either way. I’m going to figure out how and update this post at a later time.
On Linux it looks the old plugin library libjavaplugin_oji.so is no long adequate. Remove any links to them. Add new links to …/jre/lib/i386/libnpjp2.so in your ~/.mozilla/plugins directory.
If you get an executable stack error, run “execstack -c libnpjp2.so” to clear the executable stack flag on the library. Then the error should go away.
Refer to this blog.