"Unsupported Content Type" issue with JBoss Tools HTML Editor

After installing JBoss Tools 3.0.1GA from the update site http://download.jboss.org/jbosstools/updates/stable/ using the JBoss HTML Editor fails, both for creating new HTML files as well as for opening existing HTML files.

New HTML File:
1. New -> Other -> JBoss Tools Web -> HTML File
2. An empty JBoss Tools HTML Editor opens and Eclipse displays a popup saying "Unsupported content type in editor. To associate file extension with a supported content type please see content type preference page".
3. After closing the popup, the HTML editor can be used, but does not work properly: The visual editor pane is deactivated and does not display content typed in the source pane. The preview does not show the html content typed in the source pane either.

Existing HTML File:
1. Right click -> Open With -> JBoss Tools HTML Editor
2. The same popup is displayed. But in this case, the HTML Editor does not show up.
3. Instead eclipse displays an error message:

java.lang.ClassCastException: org.eclipse.core.internal.filebuffers.SynchronizableDocument cannot be cast to org.eclipse.wst.sse.core.internal.provisional.text.IStructuredDocument
at org.eclipse.wst.sse.ui.internal.provisional.style.StructuredPresentationReconciler.processDamage(StructuredPresentationReconciler.java:1070)
at org.eclipse.wst.sse.ui.internal.provisional.style.StructuredPresentationReconciler$InternalListener.inputDocumentChanged(StructuredPresentationReconciler.java:470)
at org.eclipse.jface.text.TextViewer.fireInputDocumentChanged(TextViewer.java:2714)
at org.eclipse.jface.text.TextViewer.setDocument(TextViewer.java:2763)
at org.eclipse.jface.text.source.SourceViewer.setDocument(SourceViewer.java:541)
at org.eclipse.jface.text.source.projection.ProjectionViewer.setDocument(ProjectionViewer.java:369)
at org.eclipse.wst.sse.ui.internal.StructuredTextViewer.setDocument(StructuredTextViewer.java:785)
at org.eclipse.jface.text.source.SourceViewer.setDocument(SourceViewer.java:496)
at org.eclipse.ui.texteditor.AbstractTextEditor.initializeSourceViewer(AbstractTextEditor.java:3808)
at org.eclipse.ui.texteditor.AbstractTextEditor.createPartControl(AbstractTextEditor.java:3364)
at org.eclipse.ui.texteditor.StatusTextEditor.createPartControl(StatusTextEditor.java:53)
at org.eclipse.ui.texteditor.AbstractDecoratedTextEditor.createPartControl(AbstractDecoratedTextEditor.java:394)
at org.eclipse.wst.sse.ui.StructuredTextEditor.createPartControl(StructuredTextEditor.java:1362)
at org.jboss.tools.jst.jsp.jspeditor.JSPTextEditor.createPartControl(JSPTextEditor.java:313)
at org.jboss.tools.vpe.editor.VpeEditorPart.createPartControl(VpeEditorPart.java:606)
at org.jboss.tools.jst.jsp.jspeditor.JSPMultiPageEditorPart.addPage(JSPMultiPageEditorPart.java:79)
at org.jboss.tools.jst.jsp.jspeditor.JSPMultiPageEditor.createPagesForVPE(JSPMultiPageEditor.java:474)
at org.jboss.tools.jst.jsp.jspeditor.JSPMultiPageEditor.createPages(JSPMultiPageEditor.java:409)
at org.jboss.tools.jst.jsp.jspeditor.JSPMultiPageEditorPart.createPartControl(JSPMultiPageEditorPart.java:125)
at org.eclipse.ui.internal.EditorReference.createPartHelper(EditorReference.java:661)
at org.eclipse.ui.internal.EditorReference.createPart(EditorReference.java:428)
at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:594)
at org.eclipse.ui.internal.EditorReference.getEditor(EditorReference.java:266)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditorBatched(WorkbenchPage.java:2820)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:2729)
at org.eclipse.ui.internal.WorkbenchPage.access$11(WorkbenchPage.java:2721)
at org.eclipse.ui.internal.WorkbenchPage$10.run(WorkbenchPage.java:2673)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2668)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2652)
at org.eclipse.ui.actions.OpenWithMenu.openEditor(OpenWithMenu.java:337)
at org.eclipse.ui.actions.OpenWithMenu.access$0(OpenWithMenu.java:325)
at org.eclipse.ui.actions.OpenWithMenu$2.handleEvent(OpenWithMenu.java:187)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3823)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3422)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2384)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2348)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2200)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:495)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:288)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:490)
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:193)
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:386)
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:549)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:504)
at org.eclipse.equinox.launcher.Main.run(Main.java:1236)

I checked the "content types" configuration and found two content types for the *.html extension: "HTML" and "HTML Source File" (all respective file associations are locked). The "file associations" configuration contains multiple editors for the file extension *.html, namely: JBoss HTML Editor, Aptana HTML Editor, Untitled Text Editor, Text Editor, HTML Editor. All editors are locked by content type HTML or HTML Source File or both. JBoss Tools HTML Editor is set as default.

All editors open and edit HTML files correctly - except for JBoss Tools HTML Editor.

I am happy about any advise as I would love to introduce this tool into our SE process.

Thank you.