Sounds like it could be similar to WFLY-1531 (persistence unit service should depend on the global JPA service).
We don't have the fix nailed down yet. Could you describe your environment here (number of logical/physical CPUs and OS would be helpful).
I just noticed that there are two separate issues described here (native Hibernate and EE JPA). I'm responding to the problem mentioned by Dmitri Zamysloff now.
MacPro 5,1 OS X 10.8.3 (12D78)
Darwin 12.3.0 Darwin Kernel Version 12.3.0: Sun Jan 6 22:37:10 PST 2013; root:xnu-2050.22.13~1/RELEASE_X86_64 x86_64
3,33 GHz 6-Core Intel Xeon
6 physical processors.
12 logical processors.
Java version: 1.7.0_17
A potential fix for https://issues.jboss.org/browse/WFLY-1531 has been merged to http://github.com/wildfly/wildfly. In a few days, could you try the WildFly nightly build to see if the NPE is fixed for you?
Or download WildFly 8.0.0.Alpha2 from wildfly.org which also has the same change.