我新建一个工程，不关eclipse的话，一切正常，但当我重新开它后，工程列表不见了，还报错：
java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
    at java.util.HashMap$ValueIterator.next(Unknown Source)
    at java.util.Collections$1.next(Unknown Source)
    at org.eclipse.wst.common.navigator.internal.provisional.views.NavigatorActionService.restoreState(NavigatorActionService.java:336)
    at org.eclipse.wst.common.navigator.internal.provisional.views.CommonNavigatorManager.restoreState(CommonNavigatorManager.java:107)
    at org.eclipse.wst.common.navigator.internal.provisional.views.CommonNavigator.createPartControl(CommonNavigator.java:190)
    at org.eclipse.ui.internal.ViewReference.createPartHelper(ViewReference.java:305)
    at org.eclipse.ui.internal.ViewReference.createPart(ViewReference.java:180)
    at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:552)
    at org.eclipse.ui.internal.WorkbenchPage$ActivationList.setActive(WorkbenchPage.java:3526)
    at org.eclipse.ui.internal.WorkbenchPage.restoreState(WorkbenchPage.java:2618)
    at org.eclipse.ui.internal.WorkbenchWindow.restoreState(WorkbenchWindow.java:1819)
    at org.eclipse.ui.internal.Workbench.doRestoreState(Workbench.java:2566)
    at org.eclipse.ui.internal.Workbench.restoreState(Workbench.java:1503)
    at org.eclipse.ui.internal.Workbench.access$12(Workbench.java:1491)
    at org.eclipse.ui.internal.Workbench$17.run(Workbench.java:1374)
    at org.eclipse.core.internal.runtime.InternalPlatform.run(InternalPlatform.java:1044)
    at org.eclipse.core.runtime.Platform.run(Platform.java:783)
    at org.eclipse.ui.internal.Workbench.restoreState(Workbench.java:1318)
    at org.eclipse.ui.internal.WorkbenchConfigurer.restoreState(WorkbenchConfigurer.java:183)
    at org.eclipse.ui.application.WorkbenchAdvisor.openWindows(WorkbenchAdvisor.java:700)
    at org.eclipse.ui.internal.Workbench.init(Workbench.java:1034)
    at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:1636)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:367)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:143)
    at org.eclipse.ui.internal.ide.IDEApplication.run(IDEApplication.java:103)
    at org.eclipse.core.internal.runtime.PlatformActivator$1.run(PlatformActivator.java:226)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:376)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:163)
    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:334)
    at org.eclipse.core.launcher.Main.basicRun(Main.java:278)
    at org.eclipse.core.launcher.Main.run(Main.java:973)
    at org.eclipse.core.launcher.Main.main(Main.java:948)

这是为什么？？？？[em10][em10][em10][em10]