Hello Jeanfrancois,
I finally solved this problem, and the end of the story is that the test certificate was not correctly imported into the keystore.
In my original post I had mentioned three blog/wiki entries that I had read for instructions. But the one that I actually followed was the last one (
http://blogs.sun.com/enterprisetechtips/entry/using_ssl_with_glassfish_v2), which proposes to use a small Java program to import the certificate into the keystore. This Java program seems not to work correctly in my case.
After rereading the instructions of the certificate provider I imported the certificate with keytool, and that did work. Also Firefox does now see the intermediate certificates and accepts the test certificate without any warning.
Thanks
Stephan
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