AppEngine exception

Uncaught exception from servlet
java.lang.IncompatibleClassChangeError: Implementing class
    at com.google.appengine.runtime.Request.process-c62837625532f455(Request.java)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
    at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    at com.sun.jersey.api.core.ScanningResourceConfig.init(ScanningResourceConfig.java:79)
    at com.sun.jersey.api.core.PackagesResourceConfig.init(PackagesResourceConfig.java:104)
    at com.sun.jersey.api.core.PackagesResourceConfig.<init>(PackagesResourceConfig.java:78)
    at com.sun.jersey.api.core.PackagesResourceConfig.<init>(PackagesResourceConfig.java:89)
    at com.sun.jersey.spi.container.servlet.WebComponent.createResourceConfig(WebComponent.java:696)
    at com.sun.jersey.spi.container.servlet.WebComponent.createResourceConfig(WebComponent.java:674)
    at com.sun.jersey.spi.container.servlet.WebComponent.init(WebComponent.java:203)
    at com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:374)
    at com.sun.jersey.spi.container.servlet.ServletContainer.init(ServletContainer.java:557)
    at javax.servlet.GenericServlet.init(GenericServlet.java:212)
    at org.mortbay.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:440)
    at org.mortbay.jetty.servlet.ServletHolder.doStart(ServletHolder.java:263)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:685)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
    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.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 java.lang.Thread.run(Thread.java:679)