cross domain AJAX call

cross domain AJAX call

I am attempting to make the AJAX call at the bottom of this post using JSONP

The URL is a vocab server - it takes text strings and returns search suggestions.
The (this).val() value is the content of a input box.

When I make this call from Chrome with security turned off (so that cross domain restrictions are removed) it works.

It does not work in normal mode because of the cross domain restrictions.
I cant seam to get JSONP to work.

I have tried copy/pasteing the following attributes from a different AJAX call which is working (different project and different server called) and all it does it cause the fail() function to run. and output "uncaught SyntxError : Unexpected token to the console.


dataType : 'jsonp' ,
crossDomain : true ,
jsonp : 'json.wrf'


Incase it is relevant 
when the URL in the code bellow is pasted into the browser it returns XML
When the AJAX call is made using the exact same URL (with security turned off) it returns JSON
The request header on the manual call reads : text/html,application/xhtml+xml
The request header on the ajax call read : text/plain, */* q=0.01

How can I make a JSONP call work? 
   

    

     $.
     ajax({
     
 
     method: 
     "GET",
     
 
     dataType: 
     "text",
     
 
     crossDomain: 
     true,
     
 
     url: 
     "http://vocabServerUrl/q/" + $(
     this).
     val()
     
}).done(
     function (data) {
     
 
     console.
     log(
     'ajax call has been made');
     
 
     showVocabResults(
     that, data);
     
 
     //vocabQueue.push({"key": that.attr("id"), "data": data, "element": that});
}).fail(
     function (msg) {
     
 
     alert(
     "failed: " + msg);
     
});