Olivier,
The NPE is a bug that was fixed by a check-in in mid-February - into the svn trunk, which means it is in the 3.1 builds but not the 3.0.1 builds.
I have not had a chance to build the project you made available - I do not have Eclipse installed and I have an surge of other tasks to accomplish so I will probably not get to that any time soon. Can you get Eclipse to build an EAR from your project for you? If so then you could either attach the EAR to this topic or post it at a URL as you did the project. Or you can e-mail it to me at tjquinn and the domain is dev dot java dot net.
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