Enhancing openJPA classes in Eclipse

I'm trying to enhance openJPA classes by this guide: enhancement-with-eclipse.html

For some reason the same setup works in Windows but gives this problem in Ubuntu.

Does anyone see what I'm doing wrong? I've added the persistence.xml to buildpath. I've followed the guide but I still end up with this exception:

 [openjpac] <openjpa-2.1.0-r422266:1071316 fatal user error> org.apache.openjpa.util.MetaDataException: MetaDataFactory could not be configured (conf.newMetaDataFactoryInstance() returned null). This might mean that no configuration properties were found. Ensure that you have a META-INF/persistence.xml file, that it is available in your classpath, or that the properties file you are using for configuration is available. If you are using Ant, please see the <properties> or <propertiesFile> attributes of the task's nested <config> element. This can also occur if your OpenJPA distribution jars are corrupt, or if your security policy is overly strict.
[openjpac]  at org.apache.openjpa.meta.MetaDataRepository.initializeMetaDataFactory(MetaDataRepository.java:1904)
[openjpac]  at org.apache.openjpa.meta.MetaDataRepository.endConfiguration(MetaDataRepository.java:1885)
[openjpac]  at org.apache.openjpa.lib.conf.Configurations.configureInstance(Configurations.java:518)
[openjpac]  at org.apache.openjpa.lib.conf.Configurations.configureInstance(Configurations.java:443)
[openjpac]  at org.apache.openjpa.lib.conf.PluginValue.instantiate(PluginValue.java:104)
[openjpac]  at org.apache.openjpa.conf.MetaDataRepositoryValue.instantiate(MetaDataRepositoryValue.java:68)
[openjpac]  at org.apache.openjpa.lib.conf.ObjectValue.instantiate(ObjectValue.java:83)
[openjpac]  at org.apache.openjpa.conf.OpenJPAConfigurationImpl.newMetaDataRepositoryInstance(OpenJPAConfigurationImpl.java:949)
[openjpac]  at org.apache.openjpa.ant.PCEnhancerTask.executeOn(PCEnhancerTask.java:88)
[openjpac]  at org.apache.openjpa.lib.ant.AbstractTask.execute(AbstractTask.java:171)
[openjpac]  at org.apache.开发者_如何学Gotools.ant.UnknownElement.execute(UnknownElement.java:291)
[openjpac]  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[openjpac]  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
[openjpac]  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[openjpac]  at java.lang.reflect.Method.invoke(Method.java:616)
[openjpac]  at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
[openjpac]  at org.apache.tools.ant.Task.perform(Task.java:348)
[openjpac]  at org.apache.tools.ant.Target.execute(Target.java:390)
[openjpac]  at org.apache.tools.ant.Target.performTasks(Target.java:411)
[openjpac]  at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1360)
[openjpac]  at org.apache.tools.ant.Project.executeTarget(Project.java:1329)
[openjpac]  at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
[openjpac]  at org.eclipse.ant.internal.core.ant.EclipseDefaultExecutor.executeTargets(EclipseDefaultExecutor.java:32)
[openjpac]  at org.apache.tools.ant.Project.executeTargets(Project.java:1212)
[openjpac]  at org.eclipse.ant.internal.core.ant.InternalAntRunner.run(InternalAntRunner.java:662)
[openjpac]  at org.eclipse.ant.internal.core.ant.InternalAntRunner.run(InternalAntRunner.java:495)
[openjpac]  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[openjpac]  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
[openjpac]  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[openjpac]  at java.lang.reflect.Method.invoke(Method.java:616)
[openjpac]  at org.eclipse.ant.core.AntRunner.run(AntRunner.java:378)
[openjpac]  at org.eclipse.ant.internal.ui.launchConfigurations.AntLaunchDelegate.runInSameVM(AntLaunchDelegate.java:277)
[openjpac]  at org.eclipse.ant.internal.ui.launchConfigurations.AntLaunchDelegate.launch(AntLaunchDelegate.java:239)
[openjpac]  at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:853)
[openjpac]  at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:703)
[openjpac]  at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:696)
[openjpac]  at org.eclipse.ui.externaltools.internal.model.ExternalToolBuilder.launchBuild(ExternalToolBuilder.java:179)
[openjpac]  at org.eclipse.ui.externaltools.internal.model.ExternalToolBuilder.doBuildBasedOnScope(ExternalToolBuilder.java:167)
[openjpac]  at org.eclipse.ui.externaltools.internal.model.ExternalToolBuilder.build(ExternalToolBuilder.java:86)
[openjpac]  at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:627)
[openjpac]  at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
[openjpac]  at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:170)
[openjpac]  at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:201)
[openjpac]  at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:253)
[openjpac]  at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
[openjpac]  at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:256)
[openjpac]  at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:309)
[openjpac]  at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:341)
[openjpac]  at org.eclipse.core.internal.resources.Workspace.build(Workspace.java:330)
[openjpac]  at org.eclipse.ui.actions.GlobalBuildAction$1.run(GlobalBuildAction.java:178)
[openjpac]  at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

ALL HELP GREATLY APPRECIATED!

I'd guess you've got the case wrong somewhere in the filename of your META-INF directory or persistence.xml file. Because Windows is case-insensitive, it doesn't matter there, but because UNIX cares about case, it does here.