I got the following when I closed all perspectives - then I can't do anything afterwards. Any menu action result in nothing besides a new log entry.

!ENTRY org.eclipse.ui 4 0 2009-01-27 15:06:30.180
!MESSAGE Unhandled event loop exception
!STACK 0
java.lang.NullPointerException
at org.hibernate.eclipse.jdt.ui.internal.jpa.actions.JPAMapToolActionDelegate.isCUSelected(JPAMapToolActionDelegate.java:72)
at org.hibernate.eclipse.jdt.ui.internal.jpa.actions.JPAMapToolActionDelegate.setEnabled(JPAMapToolActionDelegate.java:80)
at org.eclipse.ui.internal.handlers.HandlerProxy.setEnabled(HandlerProxy.java:220)
at org.eclipse.core.commands.Command.setEnabled(Command.java:857)
at org.eclipse.ui.menus.CommandContributionItem.isEnabled(CommandContributionItem.java:750)
at org.eclipse.ui.menus.CommandContributionItem.update(CommandContributionItem.java:486)
at org.eclipse.jface.action.MenuManager.update(MenuManager.java:870)
at org.eclipse.jface.action.MenuManager.update(MenuManager.java:870)
at org.eclipse.ui.internal.Workbench.updateActiveWorkbenchWindowMenuManager(Workbench.java:3020)
at org.eclipse.ui.internal.Workbench.access$0(Workbench.java:2980)
at org.eclipse.ui.internal.Workbench$2.bindingManagerChanged(Workbench.java:2966)
at org.eclipse.jface.bindings.BindingManager.fireBindingManagerChanged(BindingManager.java:900)
at org.eclipse.jface.bindings.BindingManager.setActiveBindings(BindingManager.java:2176)
at org.eclipse.jface.bindings.BindingManager.recomputeBindings(BindingManager.java:1742)