myeclipse4.0GA似乎必须要jdk1.5以上版本才可以（因为我开始安装了1.4后，连启动都有问题）。
我现在的环境是eclipse3.2+myeclipse4.0GA，总算可以打开了，不过在打开jsp文件时仍然有问题。
Unable to create this part due to an internal error. Reason for the failure: Widget is disposed
org.eclipse.swt.SWTException: Widget is disposed
at org.eclipse.swt.SWT.error(SWT.java:3374)
at org.eclipse.swt.SWT.error(SWT.java:3297)
at org.eclipse.swt.SWT.error(SWT.java:3268)
at org.eclipse.swt.widgets.Widget.error(Widget.java:435)
at org.eclipse.swt.widgets.Widget.checkWidget(Widget.java:330)
at org.eclipse.swt.widgets.Control.setLayoutData(Control.java:2386)
at com.genuitec.eclipse.webdesigner3.design.DesignEditSystem.createDesignView(DesignEditSystem.java:72)
at com.genuitec.eclipse.webdesigner3.WebDesigner3.createDesignView(WebDesigner3.java:73)
at com.genuitec.eclipse.webdesigner3.editors.WebDesignerMultiPageEditor.createDesignView(WebDesignerMultiPageEditor.java:392)
at com.genuitec.eclipse.webdesigner3.editors.WebDesignerMultiPageEditor.createDesignPage(WebDesignerMultiPageEditor.java:364)
at com.genuitec.eclipse.webdesigner3.editors.WebDesignerMultiPageEditor.createPages(WebDesignerMultiPageEditor.java:286)
at org.eclipse.ui.part.MultiPageEditorPart.createPartControl(MultiPageEditorPart.java:276)
at org.eclipse.ui.internal.EditorReference.createPartHelper(EditorReference.java:596)
at org.eclipse.ui.internal.EditorReference.createPart(EditorReference.java:372)
at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:566)
at org.eclipse.ui.internal.PartPane.setVisible(PartPane.java:290)
at org.eclipse.ui.internal.presentations.PresentablePart.setVisible(PresentablePart.java:140)
at org.eclipse.ui.internal.presentations.util.PresentablePartFolder.select(PresentablePartFolder.java:268)
at org.eclipse.ui.internal.presentations.util.LeftToRightTabOrder.select(LeftToRightTabOrder.java:65)
at org.eclipse.ui.internal.presentations.util.TabbedStackPresentation.selectPart(TabbedStackPresentation.java:394)
at org.eclipse.ui.internal.PartStack.refreshPresentationSelection(PartStack.java:1144)
at org.eclipse.ui.internal.PartStack.setSelection(PartStack.java:1097)
at org.eclipse.ui.internal.PartStack.showPart(PartStack.java:1311)
at org.eclipse.ui.internal.PartStack.add(PartStack.java:455)
at org.eclipse.ui.internal.EditorStack.add(EditorStack.java:102)
at org.eclipse.ui.internal.PartStack.add(PartStack.java:441)
at org.eclipse.ui.internal.EditorStack.add(EditorStack.java:111)
at org.eclipse.ui.internal.EditorSashContainer.addEditor(EditorSashContainer.java:60)
at org.eclipse.ui.internal.EditorAreaHelper.addToLayout(EditorAreaHelper.java:217)
at org.eclipse.ui.internal.EditorAreaHelper.addEditor(EditorAreaHelper.java:207)
at org.eclipse.ui.internal.EditorManager.createEditorTab(EditorManager.java:819)
at org.eclipse.ui.internal.EditorManager.openEditorFromDescriptor(EditorManager.java:718)
at org.eclipse.ui.internal.EditorManager.openEditor(EditorManager.java:679)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditorBatched(WorkbenchPage.java:2586)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:2521)
at org.eclipse.ui.internal.WorkbenchPage.access$10(WorkbenchPage.java:2513)
at org.eclipse.ui.internal.WorkbenchPage$9.run(WorkbenchPage.java:2498)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:67)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2493)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2478)
at org.eclipse.ui.ide.IDE.openEditor(IDE.java:388)
at org.eclipse.ui.ide.IDE.openEditor(IDE.java:350)
at org.eclipse.jdt.internal.ui.javaeditor.EditorUtility.openInEditor(EditorUtility.java:275)
at org.eclipse.jdt.internal.ui.javaeditor.EditorUtility.openInEditor(EditorUtility.java:139)
at org.eclipse.jdt.internal.ui.actions.OpenActionUtil.open(OpenActionUtil.java:49)
at org.eclipse.jdt.ui.actions.OpenAction.run(OpenAction.java:190)
at org.eclipse.jdt.ui.actions.OpenAction.run(OpenAction.java:174)
at org.eclipse.jdt.ui.actions.SelectionDispatchAction.dispatchRun(SelectionDispatchAction.java:267)
at org.eclipse.jdt.ui.actions.SelectionDispatchAction.run(SelectionDispatchAction.java:243)
at org.eclipse.jdt.internal.ui.packageview.PackageExplorerActionGroup.handleOpen(PackageExplorerActionGroup.java:306)
at org.eclipse.jdt.internal.ui.packageview.PackageExplorerPart$4.open(PackageExplorerPart.java:651)
at org.eclipse.jface.viewers.StructuredViewer$2.run(StructuredViewer.java:817)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:37)
at org.eclipse.core.runtime.Platform.run(Platform.java:843)
at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:44)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:149)
at org.eclipse.jface.viewers.StructuredViewer.fireOpen(StructuredViewer.java:815)
at org.eclipse.jface.viewers.StructuredViewer.handleOpen(StructuredViewer.java:1069)
at org.eclipse.jface.viewers.StructuredViewer$6.handleOpen(StructuredViewer.java:1168)
at org.eclipse.jface.util.OpenStrategy.fireOpenEvent(OpenStrategy.java:249)
at org.eclipse.jface.util.OpenStrategy.access$2(OpenStrategy.java:243)
at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:283)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:66)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:928)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3348)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:2968)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:1914)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:1878)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:419)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.IDEApplication.run(IDEApplication.java:95)
at org.eclipse.core.internal.runtime.PlatformActivator$1.run(PlatformActivator.java:78)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:92)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:68)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:400)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:177)
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.core.launcher.Main.invokeFramework(Main.java:336)
at org.eclipse.core.launcher.Main.basicRun(Main.java:280)
at org.eclipse.core.launcher.Main.run(Main.java:977)
at org.eclipse.core.launcher.Main.main(Main.java:952)
网络上搜索得到的信息是myeclipse的版本可能和eclipse存在冲突，导致myeclipse的jsp页面设计器无法正确打开，因此，在国外的论坛上，都建议还是使用eclipse3.0来写jsp。
或者，就是不要使用myeclipse的页面设计器（反正对写代码的人而言更多是使用代码视图），因此要将jsp的默认打开方式改成代码试图：
window---->perferences----->General------->editors------>file associations
选择jsp------->选择相应的editor 为default。也就是把myeclispe jsp editor 设为default（而不是myeclispe visual jsp editor）