Error performing rpcRequest

[Tatiana Vorobeva]

GWT: 2.4.0
SmartGWT: 2.4 (simple, not pro/EE - I'm just a hobbist).
Google Chrome: 17.0.963.46 (the latest version)

I have a ListGrid with custom DataSource (based on http://forums.smartclient.com/showthread.php?t=4814&page=27).
On loading the page with this grid - it tries to fetch data.
It creates service, runs executeFetch and recieves an error.

17:16:00.143 [INFO] [app] [ERROR] caught: com.google.gwt.user.client.rpc.StatusCodeException: 500 The call failed on the server; see server log for details

22:22:47.712 [ERROR] [app] 22:22:47.707:WARN:RPCManager:Error performing rpcRequest: error: FAILURE, response: {clientContext: Obj, status: -1, context: undef, startRow: 0, endRow: 0, totalRows: 0}
com.smartgwt.client.core.JsObject$SGWT_WARN: 22:22:47.707:WARN:RPCManager:Error performing rpcRequest: error: FAILURE, response: {clientContext: Obj, status: -1, context: undef, startRow: 0, endRow: 0, totalRows: 0}
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    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.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeVoid(ModuleSpace.java:289)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeVoid(JavaScriptHost.java:107)
    at com.smartgwt.client.data.DataSource.processResponse(DataSource.java)
    at ru.app.client.ui.data.datasources.ProjectInfoDS$1.onFailure(ProjectInfoDS.java:82)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:237)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:213)
    at sun.reflect.GeneratedMethodAccessor36.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
    at java.lang.Thread.run(Unknown Source)

ProjectInfo - just a simple object created for DataSource tesing (only long, String, Data). Service works with DB via ProjectInfoDao with HebarnateTemplate.
Tried to make it with gilead and without - doesn't matter.
Simple RPC service (just recieve a String from server) works fine.
"Extends", "implements", "web.xml", "appContext.xml" - are checked - everyting is done the same way as on simple (working) RPC service.

I saw in code examples that response have the following style:
response:

{clientContext: Obj, status: -1, context: undef, startRow: 0, endRow: 0, totalRows: 0}

And I have response (in Chrome):

{__gwt_ObjectId: 893, clientContext: Obj, status: -1, context: undef, startRow: 0, endRow: 0, totalRows: 0}

Questions:
1. How I can remove "__gwt_ObjectId: <id>" from response in Chrome Dev Mode?
2. (the most important) What's the reason of these errors? I can't find, why it raises this error on processing this RPC-call.