JVM Install "succeeds" but Java doesn't work in browsers.

I am having major problems getting the latest version of Java to work
on my wife's system, It apparently installs fine, either direct from
the site or off-line The test applet reports "you are using an old
version of Java techno" (the message is cut off here at the edge of
the applet's bounding box), but then goes on to report the correct,
current, version and revision number. The usual animation doesn't
appear in the test applet, and other java-requiring applets (games
etc) don't work. Symptoms are identical in IE 6.0 and a newly
installed copy of FireFox 1.5, so I don't think it's browser-related.

I am running Windows XP Home with all the latest patches and installed
the JVM with no other programs running and Norton Internet Security
disabled, rebooting and clearing the browsers' caches before and after
installation. Does anyone have any clues or suggestions?

Please respond to the Newsgroup, so that others may benefit from the exchange.
Peter R. Fletcher