I had this problem a lot when I first started using glassfish and I never came to a definite answer. It is a commons logging issue within glassfish and hibernate that the class loader has when attempting to load commons logging. I tried many things and eventually I got it to work by placing all of the hibernate jar files into glass_home/lib and not modifing and other lib inside any domain. Hope this helps because I spent some time just tinkering with both sets of libraries
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