Lotus used a Microsoft version of Java to program their rich text applets. (Naughty Iris)
If you add a new Sun Java, it can fail.
To re-enable it:
In Interent Explorer, go to Tools->Internet Options->Advanced
and deselect Use Java 2v1.4.1_03 for <applet> (requires Restart).
It doesn't seem to need a restart.
There are other version eg Java 2v1.4 1_01.