Same issue as described in parent JIRA OPENJPA-1300 and as further described in OPENJPA-1319. Providing patch OPENJPA-1320-trunk.patch. I added code to safe guard against the potential of nulls being used in the hashCode and/or equals methods, thus avoiding any potential NullPointerExceptions.
r1028456 in trunk
Closing issue which has been resolved for some time. If you believe the issue is not resolved please reopen or open a new issue.