java.lang.ClassFormatError

Error occurred during initialization of VM
java.lang.ClassFormatError: Unknown constant tag 26 in class file sun/jkernel/DownloadManager
        at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1679)
        at java.lang.Runtime.loadLibrary0(Runtime.java:823)
        at java.lang.System.loadLibrary(System.java:1029)
        at java.lang.System.initializeSystemClass(System.java:1087)