most certain possibility of this can be diagram refactoring

java.lang.classcastexception: org.eclipse.gmf.runtime.notation.impl.nodeimpl cannot be cast to org.eclipse.gmf.runtime.notation.edge
	at org.eclipse.gmf.runtime.diagram.ui.editparts.connectioneditpart.getedge(connectioneditpart.java:1154)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.connectioneditpart.refreshbendpoints(connectioneditpart.java:1215)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.connectioneditpart.refreshrouterchange(connectioneditpart.java:1266)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.connectioneditpart.installrouter(connectioneditpart.java:1208)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.connectioneditpart.addnotify(connectioneditpart.java:1084)
	at org.eclipse.gef.editparts.abstractconnectioneditpart.setparent(abstractconnectioneditpart.java:261)
	at org.eclipse.gef.editparts.abstracteditpart.addchild(abstracteditpart.java:196)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.graphicaleditpart.addchild(graphicaleditpart.java:1319)
	at org.eclipse.gef.editparts.abstracteditpart.refreshchildren(abstracteditpart.java:727)
	at org.eclipse.gef.editparts.abstracteditpart.refresh(abstracteditpart.java:677)
	at org.eclipse.gef.editparts.abstractgraphicaleditpart.refresh(abstractgraphicaleditpart.java:571)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.graphicaleditpart.access$3(graphicaleditpart.java:1)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.graphicaleditpart$3.run(graphicaleditpart.java:861)
	at org.eclipse.emf.transaction.impl.transactionaleditingdomainimpl.runexclusive(transactionaleditingdomainimpl.java:313)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.graphicaleditpart.refresh(graphicaleditpart.java:851)
	at org.eclipse.gef.editparts.abstracteditpart.addnotify(abstracteditpart.java:235)
	at org.eclipse.gef.editparts.abstractgraphicaleditpart.addnotify(abstractgraphicaleditpart.java:219)
	at org.eclipse.gef.editparts.abstracteditpart.addchild(abstracteditpart.java:198)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.graphicaleditpart.addchild(graphicaleditpart.java:1319)
	at org.eclipse.gef.editparts.abstracteditpart.refreshchildren(abstracteditpart.java:727)
	at org.eclipse.gef.editparts.abstracteditpart.refresh(abstracteditpart.java:677)
	at org.eclipse.gef.editparts.abstractgraphicaleditpart.refresh(abstractgraphicaleditpart.java:571)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.graphicaleditpart.access$3(graphicaleditpart.java:1)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.graphicaleditpart$3.run(graphicaleditpart.java:861)
	at org.eclipse.emf.transaction.impl.transactionaleditingdomainimpl.runexclusive(transactionaleditingdomainimpl.java:313)
	at org.eclipse.gmf.runtime.diagram.ui.editparts.graphicaleditpart.refresh(graphicaleditpart.java:851)
	at org.eclipse.gef.editparts.abstracteditpart.addnotify(abstracteditpart.java:235)
	at org.eclipse.gef.editparts.abstractgraphicaleditpart.addnotify(abstractgraphicaleditpart.java:219)
	at org.eclipse.gef.editparts.abstracteditpart.addchild(abstracteditpart.java:198)
	at org.eclipse.gef.editparts.simplerooteditpart.setcontents(simplerooteditpart.java:101)
	at org.eclipse.gef.ui.parts.abstracteditpartviewer.setcontents(abstracteditpartviewer.java:601)
	at org.eclipse.gmf.runtime.diagram.ui.parts.diagramgraphicalviewer.setcontents(diagramgraphicalviewer.java:378)
	at org.eclipse.gef.ui.parts.abstracteditpartviewer.setcontents(abstracteditpartviewer.java:610)
	at org.eclipse.gmf.runtime.diagram.ui.parts.diagrameditor.initializegraphicalviewercontents(diagrameditor.java:870)
	at org.eclipse.gmf.runtime.diagram.ui.parts.diagrameditor.initializegraphicalviewer(diagrameditor.java:863)
	at org.eclipse.gmf.runtime.diagram.ui.parts.diagrameditorwithflyoutpalette.initializegraphicalviewer(diagrameditorwithflyoutpalette.java:116)
	at org.eclipse.gmf.runtime.diagram.ui.resources.editor.parts.diagramdocumenteditor.initializegraphicalviewer(diagramdocumenteditor.java:175)
	at org.unicase.ui.unicasecommon.diagram.part.modeldiagrameditor.initializegraphicalviewer(modeldiagrameditor.java:127)
	at org.eclipse.gmf.runtime.diagram.ui.parts.diagrameditor.creategraphicalviewer(diagrameditor.java:807)
	at org.eclipse.gef.ui.parts.graphicaleditor.createpartcontrol(graphicaleditor.java:163)
	at org.eclipse.gmf.runtime.diagram.ui.parts.diagrameditor.createpartcontrol(diagrameditor.java:1555)
	at org.eclipse.gmf.runtime.diagram.ui.parts.diagrameditorwithflyoutpalette.createpartcontrol(diagrameditorwithflyoutpalette.java:328)
	at org.eclipse.gmf.runtime.diagram.ui.resources.editor.parts.diagramdocumenteditor.createpartcontrol(diagramdocumenteditor.java:1510)
	at org.eclipse.ui.internal.editorreference.createparthelper(editorreference.java:662)
	at org.eclipse.ui.internal.editorreference.createpart(editorreference.java:462)
	at org.eclipse.ui.internal.workbenchpartreference.getpart(workbenchpartreference.java:595)
	at org.eclipse.ui.internal.editorreference.geteditor(editorreference.java:286)
	at org.eclipse.ui.internal.workbenchpage.busyopeneditorbatched(workbenchpage.java:2857)
	at org.eclipse.ui.internal.workbenchpage.busyopeneditor(workbenchpage.java:2762)
	at org.eclipse.ui.internal.workbenchpage.access$11(workbenchpage.java:2754)
	at org.eclipse.ui.internal.workbenchpage$10.run(workbenchpage.java:2705)
	at org.eclipse.swt.custom.busyindicator.showwhile(busyindicator.java:70)
	at org.eclipse.ui.internal.workbenchpage.openeditor(workbenchpage.java:2701)
	at org.eclipse.ui.internal.workbenchpage.openeditor(workbenchpage.java:2685)
	at org.eclipse.ui.internal.workbenchpage.openeditor(workbenchpage.java:2676)
	at org.unicase.ui.unicasecommon.common.diagram.diagramopener.opendiagram(diagramopener.java:31)
	at org.unicase.ui.usecasediagram.usecasediagramopener.openmodelelement(usecasediagramopener.java:42)
	at org.unicase.ui.common.util.actionhelper.openmodelelement(actionhelper.java:135)
	at org.unicase.ui.navigator.commands.altkeydoubleclickaction.openselectedmodelelement(altkeydoubleclickaction.java:119)
	at org.unicase.ui.navigator.commands.altkeydoubleclickaction.run(altkeydoubleclickaction.java:96)
	at org.unicase.ui.navigator.commands.altkeydoubleclickaction.doubleclick(altkeydoubleclickaction.java:144)
	at org.eclipse.jface.viewers.structuredviewer$1.run(structuredviewer.java:821)
	at org.eclipse.core.runtime.saferunner.run(saferunner.java:42)
	at org.eclipse.core.runtime.platform.run(platform.java:888)
	at org.eclipse.ui.internal.jfaceutil$1.run(jfaceutil.java:48)
	at org.eclipse.jface.util.saferunnable.run(saferunnable.java:175)
	at org.eclipse.jface.viewers.structuredviewer.firedoubleclick(structuredviewer.java:819)
	at org.eclipse.jface.viewers.abstracttreeviewer.handledoubleselect(abstracttreeviewer.java:1419)
	at org.eclipse.jface.viewers.structuredviewer$4.widgetdefaultselected(structuredviewer.java:1195)
	at org.eclipse.jface.util.openstrategy.firedefaultselectionevent(openstrategy.java:238)
	at org.eclipse.jface.util.openstrategy.access$0(openstrategy.java:235)
	at org.eclipse.jface.util.openstrategy$1.handleevent(openstrategy.java:296)
	at org.eclipse.swt.widgets.eventtable.sendevent(eventtable.java:84)
	at org.eclipse.swt.widgets.display.sendevent(display.java:3543)
	at org.eclipse.swt.widgets.widget.sendevent(widget.java:1250)
	at org.eclipse.swt.widgets.widget.sendevent(widget.java:1273)
	at org.eclipse.swt.widgets.widget.sendevent(widget.java:1258)
	at org.eclipse.swt.widgets.widget.notifylisteners(widget.java:1079)
	at org.eclipse.swt.widgets.display.rundeferredevents(display.java:3441)
	at org.eclipse.swt.widgets.display.readanddispatch(display.java:3100)
	at org.eclipse.ui.internal.workbench.runeventloop(workbench.java:2405)
	at org.eclipse.ui.internal.workbench.runui(workbench.java:2369)
	at org.eclipse.ui.internal.workbench.access$4(workbench.java:2221)
	at org.eclipse.ui.internal.workbench$5.run(workbench.java:500)
	at org.eclipse.core.databinding.observable.realm.runwithdefault(realm.java:332)
	at org.eclipse.ui.internal.workbench.createandrunworkbench(workbench.java:493)
	at org.eclipse.ui.platformui.createandrunworkbench(platformui.java:149)
	at org.eclipse.ui.internal.ide.application.ideapplication.start(ideapplication.java:113)
	at org.eclipse.equinox.internal.app.eclipseapphandle.run(eclipseapphandle.java:194)
	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:368)
	at org.eclipse.core.runtime.adaptor.eclipsestarter.run(eclipsestarter.java:179)
	at sun.reflect.nativemethodaccessorimpl.invoke0(native method)
	at sun.reflect.nativemethodaccessorimpl.invoke(nativemethodaccessorimpl.java:39)
	at sun.reflect.delegatingmethodaccessorimpl.invoke(delegatingmethodaccessorimpl.java:25)
	at java.lang.reflect.method.invoke(method.java:597)
	at org.eclipse.equinox.launcher.main.invokeframework(main.java:559)
	at org.eclipse.equinox.launcher.main.basicrun(main.java:514)
	at org.eclipse.equinox.launcher.main.run(main.java:1311)
	at org.eclipse.equinox.launcher.main.main(main.java:1287)
