[ERROR] RPCManager performTransactionReply: No such transaction

hello ,
I'm using SmartGWT -4.0 and tried to run the example of using DataSource with Json , RestDataSourceWithJson.zip .
but the development mode console returns me the following error :

10:55:28.207 [ ERROR ] [ restdatasourcewithjson ] 10:55:28.214 : XRP4 : WARN : RPCManager : performTransactionReply : No such transaction 0

com.smartgwt.client.core.JsObject $ SGWT_WARN : 10:55:28.214 : XRP4 : WARN : RPCManager : performTransactionReply : No such transaction 0
at sun.reflect.NativeConstructorAccessorImpl.newInsta nce0 ( Native Method )
at sun.reflect.NativeConstructorAccessorImpl.newInsta nce ( NativeConstructorAccessorImpl.java : 57)
at sun.reflect.DelegatingConstructorAccessorImpl.newI nstance ( DelegatingConstructorAccessorImpl.java : 45)
at java.lang.reflect.Constructor.newInstance ( Constructor.java : 525 )
at com.google.gwt.dev.shell.MethodAdaptor.invoke ( MethodAdaptor.java : 105)
at com.google.gwt.dev.shell.MethodDispatch.invoke ( MethodDispatch.java : 71)
at com.google.gwt.dev.shell.OophmSessionHandler.invok e ( OophmSessionHandler.java : 172)
at com.google.gwt.dev.shell.BrowserChannelServer.reac tToMessages ( BrowserChannelServer.java : 293)
at com.google.gwt.dev.shell.BrowserChannelServer.proc essConnection ( BrowserChannelServer.java : 547)
at com.google.gwt.dev.shell.BrowserChannelServer.run ( BrowserChannelServer.java : 364 )
at java.lang.Thread.run ( Thread.java : 722 )


this happens to any other project that uses json .
has anyone had this error ?

thanks for the help .