java.lang.IllegalArgumentException: file:/C:/lib/swingx/swingx-all-1.6.4.jar/ is not a valid classpath entry; use a jar-protocol URL.
   at org.netbeans.modules.java.classpath.SimplePathResourceImplementation.verify(SimplePathResourceImplementation.java:100)
   at org.netbeans.modules.java.classpath.SimplePathResourceImplementation.verify(SimplePathResourceImplementation.java:68)
   at org.netbeans.modules.java.classpath.SimplePathResourceImplementation.<init>(SimplePathResourceImplementation.java:126)
   at org.netbeans.spi.java.classpath.support.ClassPathSupport.createResource(ClassPathSupport.java:77)
   at org.netbeans.spi.java.classpath.support.ClassPathSupport.createClassPath(ClassPathSupport.java:147)
Caused: java.lang.IllegalArgumentException: LibraryImplementation:[org.netbeans.modules.java.j2seplatform.libraries.J2SELibraryTypeProvider$J2SELibraryImpl] returned wrong root:file:/C:/lib/swingx/swingx-all-1.6.4.jar/ is not a valid classpath entry; use a jar-protocol URL.
   at org.netbeans.modules.java.j2seplatform.libraries.J2SELibraryClassPathProvider.findClassPathOrNull(J2SELibraryClassPathProvider.java:125)
   at org.netbeans.modules.java.j2seplatform.libraries.J2SELibraryClassPathProvider.findClassPath(J2SELibraryClassPathProvider.java:86)
   at org.netbeans.api.java.classpath.ClassPath.getClassPath(ClassPath.java:628)
   at org.netbeans.api.java.source.ClasspathInfo.create(ClasspathInfo.java:302)
   at org.netbeans.api.java.source.ClasspathInfo.create(ClasspathInfo.java:317)
   at org.netbeans.modules.java.source.parsing.JavacParser.init(JavacParser.java:300)
   at org.netbeans.modules.java.source.parsing.JavacParser.parseImpl(JavacParser.java:431)
   at org.netbeans.modules.java.source.parsing.JavacParser.parse(JavacParser.java:374)
   at org.netbeans.modules.parsing.impl.TaskProcessor.callParse(TaskProcessor.java:605)
   at org.netbeans.modules.parsing.impl.SourceCache.getResult(SourceCache.java:236)
   at org.netbeans.modules.parsing.api.ResultIterator.getParserResult(ResultIterator.java:138)
   at org.netbeans.modules.parsing.api.ResultIterator.getParserResult(ResultIterator.java:152)
   at org.netbeans.modules.editor.java.JavaCompletionProvider$JavaCompletionQuery$Task.run(JavaCompletionProvider.java:5699)
   at org.netbeans.modules.parsing.impl.TaskProcessor.callUserTask(TaskProcessor.java:593)
   at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:155)
   at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:139)
   at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:206)
   at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:203)
   at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:176)
   at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:360)
   at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:74)
   at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:203)
   at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:106)
   at org.netbeans.modules.editor.java.JavaCompletionProvider$JavaCompletionQuery.query(JavaCompletionProvider.java:300)
   at org.netbeans.spi.editor.completion.support.AsyncCompletionTask.run(AsyncCompletionTask.java:223)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1432)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2042)