Eclipse WindowBuilder error with NullPoInterException - eclipse

Question

The version of my eclipse is indigo.
I've installed WindowBuilder through
Help --> Insttall New Software
However, when I launch the new project with WindowBuilder
I got the following error
java.lang.NullPointerException
at org.eclipse.wb.internal.core.editor.multi.SourcePage.updateSourceActions(SourcePage.java:140)
at org.eclipse.wb.internal.core.editor.multi.SourcePage.handleActiveState(SourcePage.java:74)
at org.eclipse.wb.internal.core.editor.multi.DefaultMultiMode.showPage(DefaultMultiMode.java:125)
at org.eclipse.wb.internal.core.editor.multi.MultiPagesMode.showSource(MultiPagesMode.java:54)
at org.eclipse.wb.internal.core.editor.multi.MultiPagesMode.create(MultiPagesMode.java:100)
at org.eclipse.wb.internal.core.editor.multi.DesignerEditor.createPartControl(DesignerEditor.java:87)
at org.eclipse.ui.internal.EditorReference.createPartHelper(EditorReference.java:670)
at org.eclipse.ui.internal.EditorReference.createPart(EditorReference.java:465)
at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:595)
at org.eclipse.ui.internal.PartPane.setVisible(PartPane.java:315)
at org.eclipse.ui.internal.presentations.PresentablePart.setVisible(PresentablePart.java:180)
at org.eclipse.ui.internal.presentations.util.PresentablePartFolder.select(PresentablePartFolder.java:270)
at org.eclipse.ui.internal.presentations.util.LeftToRightTabOrder.select(LeftToRightTabOrder.java:65)
at org.eclipse.ui.internal.presentations.util.TabbedStackPresentation.selectPart(TabbedStackPresentation.java:473)
at org.eclipse.ui.internal.PartStack.refreshPresentationSelection(PartStack.java:1245)
at org.eclipse.ui.internal.PartStack.setSelection(PartStack.java:1198)
at org.eclipse.ui.internal.PartStack.showPart(PartStack.java:1597)
at org.eclipse.ui.internal.PartStack.add(PartStack.java:493)
at org.eclipse.ui.internal.EditorStack.add(EditorStack.java:103)
at org.eclipse.ui.internal.PartStack.add(PartStack.java:479)
at org.eclipse.ui.internal.EditorStack.add(EditorStack.java:112)
at org.eclipse.ui.internal.EditorSashContainer.addEditor(EditorSashContainer.java:63)
at org.eclipse.ui.internal.EditorAreaHelper.addToLayout(EditorAreaHelper.java:225)
at org.eclipse.ui.internal.EditorAreaHelper.addEditor(EditorAreaHelper.java:213)
at org.eclipse.ui.internal.EditorManager.createEditorTab(EditorManager.java:808)
at org.eclipse.ui.internal.EditorManager.openEditorFromDescriptor(EditorManager.java:707)
at org.eclipse.ui.internal.EditorManager.openEditor(EditorManager.java:666)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditorBatched(WorkbenchPage.java:2946)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:2854)
at org.eclipse.ui.internal.WorkbenchPage.access$11(WorkbenchPage.java:2846)
at org.eclipse.ui.internal.WorkbenchPage$10.run(WorkbenchPage.java:2797)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2793)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2777)
at org.eclipse.ui.actions.OpenWithMenu.openEditor(OpenWithMenu.java:338)
at org.eclipse.ui.actions.OpenWithMenu$2.handleEvent(OpenWithMenu.java:180)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1276)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3562)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3186)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2701)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2665)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2499)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:679)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:668)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
at org.eclipse.equinox.launcher.Main.main(Main.java:1414)
The following is other plugins I installed for running WindowBuilder:
Swing Designer
SWT Designer
SWT Designer Core
SWT Designer SWT_AWT Support
SWT Designer XWT Support
Usage Data Collector 1.4.0.R201106061540
WindowBuilder Core 1.3.0.r37x201202052311
WindowBuilder Core Documentation 1.3.0.r37x201202052336
WindowBuilder Core UI 1.3.0.r37x201202052340
WindowBuilder GroupLayout Support 1.3.0.r37x201202060028
WindowBuilder XML Core (requires Eclipse WTP/WST) 1.3.0.r37x201202052344
Please let me know if you know how to fix this.
Thanks.