AJAX to Sharepoint Server with Phonegap and JQuery Mobile not working

I have the following Problem. In the Phonegap App(for Android) I want to make an AJAX-Call to connect with a Sharepoint Server, with the following Code:

$.ajax({  

   url:"https://xxx/_vti_bin/lists.asmx",



   beforeSend: function( xhr ){

    xhr.setRequestHeader(

    "SOAPAction",

    "http://schemas.microsoft.com/sharepoint/soap/GetListCollection"

    );

    xhr.setRequestHeader("Content-Type","text/xml; charset=utf-8");

    }, 

   dataType:"xml",  

   contentType: "application/xml; charset=utf-8", 

   timeout:10000,  

   type:'POST', 

   cache: false,

   username: "username",

   password: "password",

   data: soapEnv,

   success:function(data) {

       // alert data

       var serializer = new XMLSerializer();

        serialized = serializer.serializeToString(data);

       alert(serialized);

   },  

   error:function(XMLHttpRequest,textStatus, errorThrown) {   

       // alert errors

     alert("Error status :"+textStatus);  

     alert("Error type :"+errorThrown);  

     alert("Error message :"+XMLHttpRequest.responseXML); 

     alert("Error statustext :"+XMLHttpRequest.statusText); 

     alert("Error request status :"+XMLHttpRequest.status); 

   }, 

   complete: function(jqXHR, textStatus){

       alert(textStatus);

   }

    });

When I try to run it on the Android Emulator the error messages are:

Error status: error   

Error type: 

Error message: undefined

Error statustext: error

Error request status: 0

However when I try to run it on my Browser (Chrome) with disabled websecurity (because of same origin policy) it works all fine. Phonegap normally shouldn't care about SOP because of the file:/// Protocol. I added the following to 'mobileinit':

$(document).bind("mobileinit", function() {

            $.support.cors = true;

            $.mobile.allowCrossDomainPages = true;

        });

But when I run the same Code in Chrome without websecurity disabled, I get exactly the same errors as in the Android Emulator.

I also tried an AJAX call to wikipedia (with html instead of xml, and GET instead of POST), and that worked without a problem.

Also I think the AJAX to Sharepoint doesn't even get fired (no traffic in Fiddler2, if I managed to configure it the right way)

So I am really stuck with this problem since 2 days now, if anyone knows how to make this ajax call work, it would made me so happy :-)

(soapEnv is the XML envelope, sent to the server)