Cannot open GWT classes with GWT Designer

I am using the GWT plugin along with GWT Designer on Eclipse 3.6. I
get the following error when trying to switch from "Source" to
"Design" view in GWT Designer:

Any suggestion would be greatly appreciated!

java.lang.NoSuchMethodError:
com.google.gdt.eclipse.designer.model.widgets.support.GwtState.getCSSFiles()Ljava/
util/List;
at
com.google.gdt.eclipse.designer.gxt.parser.ClassLoaderValidator.hasRequiredStyles(ClassLoaderValidator.java:
89)
at
com.google.gdt.eclipse.designer.gxt.parser.ClassLoaderValidator.validate(ClassLoaderValidator.java:
45)
at
com.google.gdt.eclipse.designer.parser.ParseFactory.validate(ParseFactory.java:
465)
at
com.google.gdt.eclipse.designer.parser.ParseFactory.getClassLoader(ParseFactory.java:
433)
at
org.eclipse.wb.internal.core.parser.AbstractParseFactory.initializeClassLoader(AbstractParseFactory.java:
732)
at
com.google.gdt.eclipse.designer.parser.ParseFactory.getRootContext(ParseFactory.java:
103)
at
org.eclipse.wb.internal.core.parser.JavaInfoParser.prepareParseContext(JavaInfoParser.java:
1185)
at
org.eclipse.wb.internal.core.parser.JavaInfoParser.parse(JavaInfoParser.java:
244)
at org.eclipse.wb.internal.core.parser.JavaInfoParser.access
$9(JavaInfoParser.java:240)
at org.eclipse.wb.internal.core.parser.JavaInfoParser
$1.runObject(JavaInfoParser.java:153)
at org.eclipse.wb.internal.core.parser.JavaInfoParser
$1.runObject(JavaInfoParser.java:1)
at
org.eclipse.wb.internal.core.utils.execution.ExecutionUtils.runDesignTime(ExecutionUtils.java:
153)
at
org.eclipse.wb.internal.core.parser.JavaInfoParser.parse(JavaInfoParser.java:
151)
at
org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF(DesignPage.java:
513)
at org.eclipse.wb.internal.core.editor.DesignPage.access
$9(DesignPage.java:501)
at org.eclipse.wb.internal.core.editor.DesignPage
$8$1.run(DesignPage.java:434)
at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:
179)
at
org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:
150)
at org.eclipse.swt.widgets.Display.syncExec(Display.java:4584)
at org.eclipse.wb.internal.core.editor.DesignPage
$8.run(DesignPage.java:431)
at
org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:
464)
at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:
372)
at
org.eclipse.jface.dialogs.ProgressMonitorDialog.run(ProgressMonitorDialog.java:
507)
at
org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF_withProgress(DesignPage.java:
450)
at
org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF(DesignPage.java:
400)
at
org.eclipse.wb.internal.core.editor.UndoManager.refreshDesignerEditor(UndoManager.java:
381)
at
org.eclipse.wb.internal.core.editor.UndoManager.activate(UndoManager.java:
90)
at
org.eclipse.wb.internal.core.editor.DesignPage.handleActiveState_True(DesignPage.java:
248)
at
org.eclipse.wb.internal.core.editor.DesignPage.handleActiveState(DesignPage.java:
226)
at
org.eclipse.wb.internal.core.editor.multi.DefaultMultiMode.showPage(DefaultMultiMode.java:
125)
at org.eclipse.wb.internal.core.editor.multi.DefaultMultiMode
$1.widgetSelected(DefaultMultiMode.java:63)
at
org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:
234)
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.Widget.sendEvent(Widget.java:1077)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1062)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:774)
at org.eclipse.swt.custom.CTabFolder.setSelection(CTabFolder.java:
2743)
at org.eclipse.swt.custom.CTabFolder.onMouse(CTabFolder.java:1429)
at org.eclipse.swt.custom.CTabFolder$1.handleEvent(CTabFolder.java:
257)
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:
4066)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3657)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:
2640)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2604)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2438)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:671)
at
org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:
332)
at
org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:
664)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:
149)
at
org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:
115)
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:
369)
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:619)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:574)
at org.eclipse.equinox.launcher.Main.run(Main.java:1407)
at org.eclipse.equinox.launcher.Main.main(Main.java:1383)

--
You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group.
To post to this group, send email to google-web-toolkit@googlegroups.com.
To unsubscribe from this group, send email to google-web-toolkit+unsubscribe@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.