GAE repackaged-appengine-jakarta-jstl-1.1.2.jar failed to read Warning

[user1978035 via StackOverflow]

I hava a java application on GAE (SDK 1.7.3), i randomly get in the logs a warning that i can't find the answer to, the warning just slows down the run for about 3 seconds but doesn't crash it.

The warning is :

    Failed to read file: /base/data/home/apps/s~pick-a-pic/1.364536886034809630/WEB-INF/lib/repackaged-appengine-jakarta-jstl-1.1.2.jar
    java.util.zip.ZipException: error in opening zip file
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.<init>(ZipFile.java:143)
at java.util.jar.JarFile.<init>(JarFile.java:150)
at java.util.jar.JarFile.<init>(JarFile.java:114)
at org.mortbay.jetty.webapp.TagLibConfiguration.configureWebApp(TagLibConfiguration.java:174)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1247)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.createHandler(AppVersionHandlerMap.java:219)
at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.getHandler(AppVersionHandlerMap.java:194)
at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:134)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:447)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:454)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:461)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:703)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:338)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:330)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:458)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
at java.lang.Thread.run(Thread.java:679)

How can i solve this problem ? I've already added to WEB_INF/lib this jar, it doesn't solves it..

Thank you

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