Unable to delete project

simply trying to press the "Delete" button to delete a project from the project overview.
Result (after 40 secs):

javax.jdo.JDOUserException: Cannot read fields from a deleted object
FailedObject:116182
at org.jpox.state.jdo.PersistentDeleted.transitionReadField(PersistentDeleted.java:115)
at org.jpox.state.StateManagerImpl.transitionReadField(StateManagerImpl.java:3394)
at org.jpox.state.StateManagerImpl.isLoaded(StateManagerImpl.java:1982)
at org.jpox.store.rdbms.scostore.FKListStore.validateElementForWriting(FKListStore.java:1326)
at org.jpox.store.rdbms.scostore.FKListStore.set(FKListStore.java:370)
at org.jpox.sco.List.set(List.java:1080)
at org.jpox.sco.SCOUtils.updateListWithListElements(SCOUtils.java:700)
at org.jpox.sco.List.attachCopy(List.java:426)
at org.jpox.state.AttachFieldManager.storeObjectField(AttachFieldManager.java:157)
at org.jpox.state.StateManagerImpl.providedObjectField(StateManagerImpl.java:2771)
at org.apache.maven.continuum.model.project.Project.jdoProvideField(Project.java)
at org.apache.maven.continuum.model.project.Project.jdoProvideFields(Project.java)
at org.jpox.state.StateManagerImpl.provideFields(StateManagerImpl.java:3115)
at org.jpox.state.StateManagerImpl.internalAttachCopy(StateManagerImpl.java:4389)
at org.jpox.state.StateManagerImpl.attachCopy(StateManagerImpl.java:4331)
at org.jpox.AbstractPersistenceManager.attachCopy(AbstractPersistenceManager.java:1431)
at org.jpox.state.AttachFieldManager.storeObjectField(AttachFieldManager.java:175)
at org.jpox.state.StateManagerImpl.providedObjectField(StateManagerImpl.java:2771)
at org.apache.maven.continuum.model.project.BuildResult.jdoProvideField(BuildResult.java)
at org.apache.maven.continuum.model.project.BuildResult.jdoProvideFields(BuildResult.java)
at org.jpox.state.StateManagerImpl.provideFields(StateManagerImpl.java:3115)
at org.jpox.state.StateManagerImpl.internalAttachCopy(StateManagerImpl.java:4389)
at org.jpox.state.StateManagerImpl.attachCopy(StateManagerImpl.java:4331)
at org.jpox.AbstractPersistenceManager.attachCopy(AbstractPersistenceManager.java:1431)
at org.jpox.AbstractPersistenceManager.internalMakePersistent(AbstractPersistenceManager.java:1161)
at org.jpox.AbstractPersistenceManager.makePersistent(AbstractPersistenceManager.java:1277)
at org.apache.maven.continuum.store.JdoContinuumStore.updateBuildResult(JdoContinuumStore.java:391)
at org.apache.maven.continuum.DefaultContinuum.removeProject(DefaultContinuum.java:770)
at org.apache.maven.continuum.web.action.DeleteProjectAction.execute(DeleteProjectAction.java:54)

the project hasn'teben been deleted.