Thanks Oscar, below is the trace
Problems occurred when invoking code from plug-in: "org.eclipse.ui.workbench".
java.lang.NullPointerException
at com.ibm.workplace.noteswc.statusbar.NotesStatusBarManager$3.perspectiveActivated(Unknown Source)
at org.eclipse.ui.internal.PerspectiveListenerList$1.run(Unknown Source)
at org.eclipse.core.runtime.SafeRunner.run(Unknown Source)
at org.eclipse.core.runtime.Platform.run(Unknown Source)
at org.eclipse.ui.internal.PerspectiveListenerList.fireEvent(Unknown Source)
at org.eclipse.ui.internal.PerspectiveListenerList.firePerspectiveActivated(Unknown Source)
at org.eclipse.ui.internal.WorkbenchWindow.firePerspectiveActivated(Unknown Source)
at org.eclipse.ui.internal.WorkbenchPage.setPerspective(Unknown Source)
at org.eclipse.ui.internal.WorkbenchPage.busySetPerspective(Unknown Source)
at org.eclipse.ui.internal.WorkbenchPage.access$16(Unknown Source)
at org.eclipse.ui.internal.WorkbenchPage$18.run(Unknown Source)
at org.eclipse.swt.custom.BusyIndicator.showWhile(Unknown Source)
at org.eclipse.ui.internal.WorkbenchPage.setPerspective(Unknown Source)
at com.ibm.rcp.platform.personality.internal.actions.PerspectiveAction.run(Unknown Source)
at com.ibm.rcp.platform.personality.internal.widgets.TabFolderContributionItem.handleWidgetSelection(Unknown Source)
at com.ibm.rcp.platform.personality.internal.widgets.TabFolderContributionItem.access$3(Unknown Source)
at com.ibm.rcp.platform.personality.internal.widgets.TabFolderContributionItem$3.widgetSelected(Unknown Source)
at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source)
at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Widget.notifyListeners(Unknown Source)
at com.ibm.rcp.swt.swidgets.STabFolder.setSelection(Unknown Source)
at com.ibm.rcp.swt.swidgets.STabFolder.onMouse(Unknown Source)
at com.ibm.rcp.swt.swidgets.STabFolder$1.handleEvent(Unknown Source)
at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
at org.eclipse.ui.internal.Workbench.runEventLoop(Unknown Source)
at org.eclipse.ui.internal.Workbench.runUI(Unknown Source)
at org.eclipse.ui.internal.Workbench.access$4(Unknown Source)
at org.eclipse.ui.internal.Workbench$5.run(Unknown Source)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Unknown Source)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Unknown Source)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(Unknown Source)
at com.ibm.rcp.personality.framework.internal.RCPApplication.run(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.internal.app.EclipseAppContainer.callMethodWithException(Unknown Source)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(Unknown Source)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(Unknown Source)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(Unknown Source)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(Unknown Source)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Unknown Source)
at org.eclipse.equinox.launcher.Main.basicRun(Unknown Source)
at org.eclipse.equinox.launcher.Main.run(Unknown Source)
at com.ibm.rcp.core.internal.launcher.Main.startLaunch(Unknown Source)
at com.ibm.rcp.core.internal.launcher.Main.main(Unknown Source)
at com.ibm.rcp.core.internal.launcher.Main.run(Unknown Source)