Problems occurred when invoking code from plug-in: "org.eclipse.jface"

Problems occurred when invoking code from plug-in: "org.eclipse.jface"

I'm working on Graphical Modelling Framework. I create one diagram file by
using GMF and launch it in eclipse running application but when i select
some items of this diagram file, I get this error:
An error has occurred. See error log for more details.
org/eclipse/gmf/runtime/gef/ui/internal/parts/CellEditorEx.
for more explanation, my created diagram file contains one class with one
Neme feature. when i select my class as one object and want to change Name
feature, i get above error. can every one help me? i don't know why this
error occur?!in fact, this error is related to my eclipse or is about one
mistake in my project!Thanks.
-------------details:----------------------
in my error log : Problems occurred when invoking code from plug-in:
"org.eclipse.jface".
Exception stack trace:
java.lang.NoClassDefFoundError:
org/eclipse/gmf/runtime/gef/ui/internal/parts/CellEditorEx
at
org.eclipse.gmf.runtime.diagram.ui.editpolicies.LabelDirectEditPolicy.getDirectEditCommand(LabelDirectEditPolicy.java:67)
at
org.eclipse.gef.editpolicies.DirectEditPolicy.getCommand(DirectEditPolicy.java:59)
at
org.eclipse.gef.editparts.AbstractEditPart.getCommand(AbstractEditPart.java:502)
at
org.eclipse.gmf.runtime.diagram.ui.editparts.GraphicalEditPart.access$1(GraphicalEditPart.java:1)
at
org.eclipse.gmf.runtime.diagram.ui.editparts.GraphicalEditPart$1.run(GraphicalEditPart.java:482)
at
org.eclipse.emf.transaction.impl.TransactionalEditingDomainImpl.runExclusive(TransactionalEditingDomainImpl.java:328)
at
org.eclipse.gmf.runtime.diagram.ui.editparts.GraphicalEditPart.getCommand(GraphicalEditPart.java:477)
at org.eclipse.gef.tools.DirectEditManager.commit(DirectEditManager.java:144)
at
org.eclipse.gmf.tooling.runtime.directedit.DirectEditManagerBase.commit(DirectEditManagerBase.java:304)
at
org.eclipse.gef.tools.DirectEditManager$4.applyEditorValue(DirectEditManager.java:298)
at org.eclipse.jface.viewers.CellEditor$1.run(CellEditor.java:335)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:49)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
at
org.eclipse.jface.viewers.CellEditor.fireApplyEditorValue(CellEditor.java:333)
at
org.eclipse.jface.viewers.TextCellEditor.handleDefaultSelection(TextCellEditor.java:293)
at
org.eclipse.jface.viewers.TextCellEditor$1.widgetDefaultSelected(TextCellEditor.java:148)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:119)
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)
at org.eclipse.equinox.launcher.Main.main(Main.java:1386)
Caused by: java.lang.ClassNotFoundException:
org.eclipse.gmf.runtime.gef.ui.internal.parts.CellEditorEx 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) ... 43 more