There is persistence.xml location problem in j2se project with eclipselink canonical processor.
Some workaround is required.
For reference - there are no problems in ejb/web/app client project, only j2se require a workaround.
fixed, but keep open for possible review, current implementation is similar to one from web project
*** Bug 181567 has been marked as a duplicate of this bug. ***
no feedback yet, mark as fixed, feel free to comment/reopen if any problem.