I've tried this John.
On Sun web site I've just found this which could be an explanation ->

Note concerning Red Hat 7: The Java 2 Runtime Environment v1.2.2 will not work with Red Hat 7. Users who want to run the Java 2 Runtime Environment on Red Hat 7 can try using new version Java 2 Runtime Environment v1.3.0 for Linux. The Java 2 Runtime Environment v1.3.0 was tested on Red Hat 6.1 and is not officially supported on Red Hat 7, but there are no known problems with running the Java 2 Runtime Environment v1.3.0 on Red Hat 7 as long as the Classic VM is not used.

So, someone know what means "as long as the Classic VM is not used" ??