Java APIs

When trying to compile any java file using javac (in HP-UX) I get the message below. It seems that the rt.jar file is corrupted, but its time stamp on the file is from a year ago, and it worked fine a week ago. Any ideas?

Here is the error message I get:

$javac AClass.java
An exception has occurred in the compiler (1.4.2.17). Please file a bug at the Java Developer Connection (http://java.sun.com/cgi-bin/bugreport.cgi) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you.
java.lang.InternalError: jzentry == 0,
jzfile = 184400,
total = 9429,
name = /opt/java1.4/jre/lib/rt.jar,
i = 382,
message = invalid LOC header (bad signature)
at java.util.zip.ZipFile$2.nextElement(ZipFile.java:338)
at com.sun.tools.javac.v8.code.ClassReader.openArchive(ClassReader.java:975)
at com.sun.tools.javac.v8.code.ClassReader.list(ClassReader.java:1218)
at com.sun.tools.javac.v8.code.ClassReader.listAll(ClassReader.java:1340)
at com.sun.tools.javac.v8.code.ClassReader.fillIn(ClassReader.java:1358)
at com.sun.tools.javac.v8.code.ClassReader.complete(ClassReader.java:1052)
at com.sun.tools.javac.v8.code.Symbol.complete(Symbol.java:372)
at com.sun.tools.javac.v8.comp.Enter.visitTopLevel(Enter.java:467)
at com.sun.tools.javac.v8.tree.Tree$TopLevel.accept(Tree.java:390)
at com.sun.tools.javac.v8.comp.Enter.classEnter(Enter.java:442)
at com.sun.tools.javac.v8.comp.Enter.classEnter(Enter.java:456)
at com.sun.tools.javac.v8.comp.Enter.complete(Enter.java:596)
at com.sun.tools.javac.v8.comp.Enter.main(Enter.java:582)
at com.sun.tools.javac.v8.JavaCompiler.compile(JavaCompiler.java:331)
at com.sun.tools.javac.v8.Main.compile(Main.java:598)
at com.sun.tools.javac.Main.compile(Main.java:36)
at com.sun.tools.javac.Main.main(Main.java:27)