[CentOS] java annoyances

Fresh install on a brand new box (Dell Precision 3500) of 5.6. I install
Sun java-1.6.0_26-b03, Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02,
mixed mode)

Then
ln -s
/usr/lib/jvm/java-1.6.0-sun-1.6.0.26.x86_64/jre/lib/amd64/libnpjp2.so
/usr/lib64/mozilla/plugins

about:plugins shows java enabled (oddly enough, I seem to have flash,
32-bit, in the 32 bit libs, and that doesn't show; guess I need to install
nspluginwrapper). I go to the java tester, as recommended on the CentOS
wiki, <http://javatester.org/version.html>, no pink rectangle, and if I
click on the enabled link, firefox crashes, with
firefox --no-remote -P
Exception in thread "main" java.lang.NoClassDefFoundError:
sun/plugin2/main/server/MozillaPlugin
Caused by: java.lang.ClassNotFoundException:
sun.plugin2.main.server.MozillaPlugin
        at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Segmentation fault

Anyone got any ideas what's wrong? Clues for the poor?

   mark