Problem with GWT 2.4 rc1 RequestFactory on tomcat

We have our gwt application working fine on the development mode with gwt 2.4rc1 but when we deployed on tomcat 6 we get the following exception on the server side when the first requestfactory call is made.

java.lang.NullPointerException
    at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
    at com.google.web.bindery.requestfactory.server.ServiceLayerCache.getOrCache(ServiceLayerCache.java:225)
    at com.google.web.bindery.requestfactory.server.ServiceLayerCache.resolveRequestFactory(ServiceLayerCache.java:198)
    at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:203)
    at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:127)
    at com.google.web.bindery.requestfactory.server.RequestFactoryServlet.doPost(RequestFactoryServlet.java:133)
    at com.sample.ads.server.service.AdsRequestFactoryServlet.doPost(AdsRequestFactoryServlet.java:42)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServ开发者_JS百科let.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
    at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
    at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
    at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:776)
    at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:705)
    at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:898)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
    at java.lang.Thread.run(Thread.java:662)

On the client side, 500 (Internal Server Error)

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The wire format has changed between GWT 2.3 and 2.4 to support obfuscated (and therefore much shortened) type identifiers. You have a 2.3 client trying to talk to the 2.4 server and there's a bug in the RC1 that makes that case fail in an unhelpful manner. The fix is to recompile your client code against the updated requestfactory code.

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In order to have an android app working with google app engine, you must create the App Engine connected Android project in Eclipse with GWT 2.3.0 configurated by default:

Windows -> Preferences -> Google -> Web Toolkit (and not 2.4.0rc1)

If you try change the GWT version from 2.4.0rc1 to 2.3.0 after having created a project, you will always have this error with the android app (web app will work)