Sorry can't shed any light on this, other than the code where this came out of, worked fine with 2.3.7_02. I had to upgrade to 2.3.7_12 to pickup the fix for wildcard search on index, and now get this.
[ObjectDB 2.3.7_12] Unexpected exception (Error 990) Generated by Java HotSpot(TM) 64-Bit Server VM 1.6.0_21 (on Linux 3.0.0-16-generic). Please report this error on http://www.objectdb.com/database/issue/new com.objectdb.o.InternalException: java.lang.NullPointerException: null java.lang.NullPointerException at com.objectdb.o.TAI.C(TAI.java:275) at com.objectdb.o.TAI.UV(TAI.java:234) at com.objectdb.o.RTT.G(RTT.java:267) at com.objectdb.o.RTT.F(RTT.java:249) at com.objectdb.o.RST.C(RST.java:180) at com.objectdb.o.RTT.l(RTT.java:134) at com.objectdb.o.RST.l(RST.java:24) at com.objectdb.o.TSK.i(TSK.java:146) at com.objectdb.o.TSK.f(TSK.java:95) at com.objectdb.o.MST.U3(MST.java:626) at com.objectdb.o.MVP.aa(MVP.java:569) at com.objectdb.o.MVP.U3(MVP.java:502) at com.objectdb.o.TAI.A(TAI.java:200) at com.objectdb.o.TAI.Ut(TAI.java:134) at com.objectdb.o.PRG.ag(PRG.java:679) at com.objectdb.o.PRG.af(PRG.java:553) at com.objectdb.o.QRM.U5(QRM.java:262) at com.objectdb.o.MST.U5(MST.java:947) at com.objectdb.o.WRA.U5(WRA.java:290) at com.objectdb.o.WSM.U5(WSM.java:113) at com.objectdb.o.QRR.g(QRR.java:232) at com.objectdb.o.QRR.b(QRR.java:151) at com.objectdb.jpa.JpaQuery.getSingleResult(JpaQuery.java:716) at sun.reflect.GeneratedMethodAccessor62.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.orm.jpa.SharedEntityManagerCreator$DeferredQueryInvocationHandler.invoke(SharedEntityManagerCreator.java:310) at $Proxy56.getSingleResult(Unknown Source) at com.contextspace.dao.party.impl.EntitlementDAOImpl.GetEntitlementForRole(EntitlementDAOImpl.java:198) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:309) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:196) at $Proxy21.GetEntitlementForRole(Unknown Source) at com.contextspace.dao.party.impl.objectdb.EntitlementDAOImplTest.SearchEntitlementByRelationships(EntitlementDAOImplTest.java:860) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31) at org.junit.runners.ParentRunner.run(ParentRunner.java:236) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)