为什么Intellij IDEA突然不再识别测试文件夹中的测试？

自从启动此项目以来，我一直在使用JUnit，并且一切正常。我有数百个测试，当然，在这里和那里，我都开始了。右键单击根测试文件夹，使用JUnit运行（或调试）。但是从昨天开始，当我这样做时，结果是：

Process finished with exit code 0

无需开始任何测试。文件夹树中的任何文件夹都是相同的。我仍然可以运行一个测试类，但是我确实需要一个选项来启动它们。如果您有任何想法，请将其放在此处。

这是我尝试运行测试时记录的内容：

2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - IntelliJ IDEA 11.1.2  Build #IU-117.418 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - JDK: 1.6.0_31 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - VM: Java HotSpot(TM) Client VM 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - Vendor: Sun Microsystems Inc. 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - OS: Windows 7 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - Last Action: RunClass 
2012-10-31 15:16:55,693 [2727217]  ERROR - m.intellij.util.ExecutorsQuery - com.intellij.psi.tree.IFileElementType cannot be cast to com.intellij.psi.tree.IStubFileElementType 
java.lang.ClassCastException: com.intellij.psi.tree.IFileElementType cannot be cast to com.intellij.psi.tree.IStubFileElementType
    at com.intellij.psi.impl.source.PsiFileImpl.calcStubTree(PsiFileImpl.java:976)
    at com.intellij.psi.stubs.StubIndexImpl$1.perform(StubIndexImpl.java:239)
    at com.intellij.psi.stubs.StubIndexImpl$1.perform(StubIndexImpl.java:220)
    at com.intellij.util.indexing.ValueContainer.forEach(ValueContainer.java:60)
    at com.intellij.psi.stubs.StubIndexImpl.process(StubIndexImpl.java:220)
    at com.intellij.psi.stubs.StubIndexImpl.get(StubIndexImpl.java:194)
    at com.intellij.psi.stubs.AbstractStubIndex.get(AbstractStubIndex.java:33)
    at com.intellij.psi.impl.java.stubs.index.JavaAnnotationIndex.get(JavaAnnotationIndex.java:47)
    at com.intellij.psi.impl.search.AnnotatedElementsSearcher.a(AnnotatedElementsSearcher.java:93)
    at com.intellij.psi.impl.search.AnnotatedElementsSearcher.execute(AnnotatedElementsSearcher.java:44)
    at com.intellij.psi.impl.search.AnnotatedElementsSearcher.execute(AnnotatedElementsSearcher.java:28)
    at com.intellij.util.ExecutorsQuery.processResults(ExecutorsQuery.java:42)
    at com.intellij.util.AbstractQuery.forEach(AbstractQuery.java:67)
    at com.intellij.util.InstanceofQuery.forEach(InstanceofQuery.java:54)
    at com.intellij.execution.ConfigurationUtil.addAnnotatedMethodsAnSubclasses(ConfigurationUtil.java:97)
    at com.intellij.execution.ConfigurationUtil.findAllTestClasses(ConfigurationUtil.java:77)
    at com.intellij.execution.junit.TestPackage$MySearchForTestsTask.run(TestPackage.java:397)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl$TaskRunnable.run(ProgressManagerImpl.java:469)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl$2.run(ProgressManagerImpl.java:178)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:218)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:169)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl$8.run(ProgressManagerImpl.java:378)
    at com.intellij.openapi.application.impl.ApplicationImpl$6.run(ApplicationImpl.java:434)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
    at java.util.concurrent.FutureTask.run(FutureTask.java:138)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:662)
    at com.intellij.openapi.application.impl.ApplicationImpl$1$1.run(ApplicationImpl.java:145)