An exception throwed by eclipse when do the new gwt project

I am newly to GWT and I started to learn it through gwt2.4. Firstly, I installed the eclipse plugin, after that, I saw the icon in the toolbar of the eclipse.

When I click the New Web Application Project, it reported an Exception. The detailed stack-trace is below.

eclipse.buildId=M20110909-1335 java.version=1.6.0_33 java.vendor=Sun Microsystems Inc. BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=en_US Framework arguments: -product org.eclipse.epp.package.java.product Command-line arguments: -os win32 -ws win32 -arch x86 -product org.eclipse.epp.package.java.product

Error Mon Jan 21 17:18:28 CST 2013 Unhandled event loop exception

java.lang.NoClassDefFoundError: com/google/gdt/eclipse/platform/shared/ui/IPixelConverter at com.google.gdt.eclipse.suite.actions.NewWebAppToolbarHandler.execute(NewWebAppToolbarHandler.java:27) at org.eclipse.ui.internal.handlers.HandlerProxy.execute(HandlerProxy.java:293) at org.eclipse.core.commands.Command.executeWithChecks(Command.java:476) at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:508) at org.eclipse.ui.internal.handlers.HandlerService.executeCommand(HandlerService.java:169) at org.eclipse.ui.internal.handlers.SlaveHandlerService.executeCommand(SlaveHandlerService.java:241) at org.eclipse.ui.menus.CommandContributionItem.handleWidgetSelection(CommandContributionItem.java:829) at org.eclipse.ui.menus.CommandContributionItem.access$19(CommandContributionItem.java:815) at org.eclipse.ui.menus.CommandContributionItem$5.handleEvent(CommandContributionItem.java:805) at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053) at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4165) at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3754) at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2696) at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2660) at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2494) at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:674) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:667) at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149) at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:123) 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:344) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179) 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(Main.java:622) at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577) at org.eclipse.equinox.launcher.Main.run(Main.java:1410) Caused by: java.lang.ClassNotFoundException: com.google.gdt.eclipse.platform.shared.ui.IPixelConverter at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:513) at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:429) at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:417) at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107) at java.lang.ClassLoader.loadClass(Unknown Source) ... 33 more

I have no idea How it happens, I tried two methods for installing the gwt plugin. One is to use the link file and the other is to put the corresponding file into the plugins and features directory. But the same exception is reported.

Why the class cannot be founded, I have searched in the plugins directory and found this class in the jar called com.google.gdt.eclipse.platform.shared_3.1.3.v201212122040-rel-r37.jar.

Who can help, thank you very much!!

Wipe out your eclipse installation and workspace. Download the eclipse zip file and start over.

Do not use Eclipse's uninstall plugin feature.