JQuery AJAX and WCF error after POST request

I am trying to send some JSON to my WCF services from a $ .ajax request. Here's my set of parameters:

$.ajax(
{
 type: "POST",
 url: theurl,
 data: '{name:"Gabriel"}',
 dataType: "json",
 async:false,
 timeout: 5000,
 //success and error callbacks here...

      

        
        
        
      

    

The WCF method contract looks like this:

[OperationContract]
        [WebInvoke(Method = "*", 
                   RequestFormat = WebMessageFormat.Json,
                   BodyStyle = WebMessageBodyStyle.Bare,
                   UriTemplate = "/Sample/POST")]
        string postSample(Stream jsondata);

      

        
        
        
      

    

WCF runs on a remote server (cross-domain and Access-Control-Allow-Origin features are available here). When I debug using w3wp.exe I can see that WCF methods get through, POST body is correct, but after service method returns (plain JSON or empty string) I get

[Exception... "Failure"...> :: line 4"  data: no]

      

        
        
        
      

    

in Firefox. Safari and Chrome throws:

Error: NETWORK_ERR: XMLHttpRequest Exception 101

      

        
        
        
      

    

I am using VS2010 and jQuery 1.7.xx

Any idea what I am doing wrong? Any suggestion would be really appreciated.