Flex - Error Message

Hey, I have Eclipse Ganymede with a Flex Builder Plugin installed:

I am getting this message when I open up an mxml file,

Could not open the editor: Assertion failed:
org.eclipse.jface.util.Assert$AssertionFailedExcep tion: Assertion failed:
at org.eclipse.jface.util.Assert.isTrue(Assert.java:1 85)
at org.eclipse.jface.util.Assert.isTrue(Assert.java:1 70)
at com.adobe.flexbuilder.editors.derived.editor.FlexM ultiPageEditorPart.setActivePage(FlexMultiPageEdit orPart.java:569)
at com.adobe.flexbuilder.editors.common.editor.CodeAn dDesignEditor.setActivePage(CodeAndDesignEditor.ja va:643)
at com.adobe.flexbuilder.editors.mxml.MXMLEditor.setA ctivePage(MXMLEditor.java:483)
at com.adobe.flexbuilder.editors.derived.editor.FlexM ultiPageEditorPart.createPartControl(FlexMultiPage EditorPart.java:235)
at com.adobe.flexbuilder.editors.common.editor.CodeAn dDesignEditor.createPartControl(CodeAndDesignEdito r.java:162)
at org.eclipse.ui.internal.EditorReference.createPart Helper(EditorReference.java:661)
at org.eclipse.ui.internal.EditorReference.createPart (EditorReference.java:428)
at org.eclipse.ui.internal.WorkbenchPartReference.get Part(WorkbenchPartReference.java:594)
at org.eclipse.ui.internal.PartPane.setVisible(PartPa ne.java:306)
at org.eclipse.ui.internal.presentations.PresentableP art.setVisible(PresentablePart.java:180)
at org.eclipse.ui.internal.presentations.util.Present ablePartFolder.select(PresentablePartFolder.java:2 70)
at org.eclipse.ui.internal.presentations.util.LeftToR ightTabOrder.select(LeftToRightTabOrder.java:65)
at org.eclipse.ui.internal.presentations.util.TabbedS tackPresentation.selectPart(TabbedStackPresentatio n.java:473)
at org.eclipse.ui.internal.PartStack.refreshPresentat ionSelection(PartStack.java:1256)
at org.eclipse.ui.internal.PartStack.setSelection(Par tStack.java:1209)
at org.eclipse.ui.internal.PartStack.showPart(PartSta ck.java:1608)
at org.eclipse.ui.internal.PartStack.add(PartStack.ja va:499)
at org.eclipse.ui.internal.EditorStack.add(EditorStac k.java:103)
at org.eclipse.ui.internal.PartStack.add(PartStack.ja va:485)
at org.eclipse.ui.internal.EditorStack.add(EditorStac k.java:112)
at org.eclipse.ui.internal.EditorSashContainer.addEdi tor(EditorSashContainer.java:63)
at org.eclipse.ui.internal.EditorAreaHelper.addToLayo ut(EditorAreaHelper.java:217)
at org.eclipse.ui.internal.EditorAreaHelper.addEditor (EditorAreaHelper.java:207)
at org.eclipse.ui.internal.EditorManager.createEditor Tab(EditorManager.java:779)
at org.eclipse.ui.internal.EditorManager.openEditorFr omDescriptor(EditorManager.java:678)
at org.eclipse.ui.internal.EditorManager.openEditor(E ditorManager.java:639)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEdit orBatched(WorkbenchPage.java:2817)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEdit or(WorkbenchPage.java:2729)
at org.eclipse.ui.internal.WorkbenchPage.access$11(Wo rkbenchPage.java:2721)
at org.eclipse.ui.internal.WorkbenchPage$10.run(Workb enchPage.java:2673)
at org.eclipse.swt.custom.BusyIndicator.showWhile(Bus yIndicator.java:70)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(W orkbenchPage.java:2668)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(W orkbenchPage.java:2652)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(W orkbenchPage.java:2643)
at org.eclipse.ui.ide.IDE.openEditor(IDE.java:646)
at org.eclipse.ui.ide.IDE.openEditor(IDE.java:605)
at org.eclipse.ui.actions.OpenFileAction.openFile(Ope nFileAction.java:99)
at org.eclipse.ui.actions.OpenSystemEditorAction.run( OpenSystemEditorAction.java:99)
at org.eclipse.ui.views.navigator.OpenActionGroup.run DefaultAction(OpenActionGroup.java:125)
at org.eclipse.ui.views.navigator.MainActionGroup.run DefaultAction(MainActionGroup.java:329)
at org.eclipse.ui.views.navigator.ResourceNavigator.h andleOpen(ResourceNavigator.java:716)
at org.eclipse.ui.views.navigator.ResourceNavigator$6 .open(ResourceNavigator.java:443)
at org.eclipse.jface.viewers.StructuredViewer$2.run(S tructuredViewer.java:820)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner .java:37)
at org.eclipse.core.runtime.Platform.run(Platform.jav a:880)
at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil. java:48)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnab le.java:175)
at org.eclipse.jface.viewers.StructuredViewer.fireOpe n(StructuredViewer.java:818)
at org.eclipse.jface.viewers.StructuredViewer.handleO pen(StructuredViewer.java:1079)
at org.eclipse.jface.viewers.StructuredViewer$6.handl eOpen(StructuredViewer.java:1183)
at org.eclipse.jface.util.OpenStrategy.fireOpenEvent( OpenStrategy.java:263)
at org.eclipse.jface.util.OpenStrategy.access$2(OpenS trategy.java:257)
at org.eclipse.jface.util.OpenStrategy$1.handleEvent( OpenStrategy.java:297)
at org.eclipse.swt.widgets.EventTable.sendEvent(Event Table.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.ja va:1003)
at org.eclipse.swt.widgets.Display.runDeferredEvents( Display.java:3823)
at org.eclipse.swt.widgets.Display.readAndDispatch(Di splay.java:3422)
at org.eclipse.ui.internal.Workbench.runEventLoop(Wor kbench.java:2384)
at org.eclipse.ui.internal.Workbench.runUI(Workbench. java:2348)
at org.eclipse.ui.internal.Workbench.access$4(Workben ch.java:2200)
at org.eclipse.ui.internal.Workbench$5.run(Workbench. java:495)
at org.eclipse.core.databinding.observable.Realm.runW ithDefault(Realm.java:288)
at org.eclipse.ui.internal.Workbench.createAndRunWork bench(Workbench.java:490)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(Pl atformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplica tion.start(IDEApplication.java:113)
at org.eclipse.equinox.internal.app.EclipseAppHandle. run(EclipseAppHandle.java:193)
at org.eclipse.core.runtime.internal.adaptor.EclipseA ppLauncher.runApplication(EclipseAppLauncher.java: 110)
at org.eclipse.core.runtime.internal.adaptor.EclipseA ppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.ru n(EclipseStarter.java:386)
at org.eclipse.core.runtime.adaptor.EclipseStarter.ru n(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknow n Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Un known Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework( Main.java:549)
at org.eclipse.equinox.launcher.Main.basicRun(Main.ja va:504)
at org.eclipse.equinox.launcher.Main.run(Main.java:12 36)
at org.eclipse.equinox.launcher.Main.main(Main.java:1 212)

"How do I fix this problem?"

are you using it on windows 7 32 bit/ 64 bit? i think you should try the other available plugin.,,