Javascript ajax requests for logout

Hi,

Using this tutorial: http://tylerfrankenstein.com/code/android-app-with-drupal-7-services-pho... and this: https://drupal.org/node/2013781 and this: http://www.anexusit.com/blog/drupal-7-services-3x-client-authentication-..., and adapting to my own needs, I was able to get the token, connect to the system and login whenever I click my user interface login. So far so good...

but when I try to logout, I get an error:
POST http://host/rest/user/logout.json 401 Unauthorized: CSRF validation failed 39ms
{"readyState":4,"responseText":"[\"CSRF validation failed\"]","responseJSON":["CSRF validation failed"],"status":401,"statusText":"Unauthorized: CSRF validation failed"}
sessio...7331901 (Zeile 170)
"error"
sessio...7331901 (Zeile 171)
"Unauthorized: CSRF validation failed"

This is my code:

//if logged in
try {

	//Do Logout!!
	//Now, proceed the logout!
	$.ajax({
		url: urlPath + 'backbone/rest/user/logout',
		type: 'post',
		//data : 'Cookie:' +userData.session_name + '=' + userData.sessid ,
		dataType: 'json',
		
		//Trying everything I can think off...
		beforeSend: function (request) {
			request.setRequestHeader("X-CSRF-Token", this.token);
		},
		error: function(XMLHttpRequest, textStatus, errorThrown){
			//alert('tf_logout_button - failed to logout');
			console.log(JSON.stringify(XMLHttpRequest));
			console.log(JSON.stringify(textStatus));
			console.log(JSON.stringify(errorThrown));
		},
		success: function(data){
			//success code
			console.log('Seams we have a success!', data);
			//session ID
			$.cookie(data.session_name, data.sessid);
			console.log( "session name: " + data.session_name + " sessid: " + data.sessid);
			//userID
			$.cookie('userId', data.user.uid);
			console.log('userId: ', data.user.uid);
			this.userId = data.user.uid;

			//populate AppSettingsModel
			that.populateAppSettings(data);
		}
	});
}
catch (error) {
	alert("tf_logout_button - " + error);
}

I can't think of more to test out... I've changed type to get, and it gives:

{"readyState":4,"responseText":"[\"Access denied for user admin\"]","responseJSON":["Access denied for user admin"],"status":401,"statusText":"Unauthorized: Access denied for user admin"}
sessio...7263504 (Zeile 172)
"error"
sessio...7263504 (Zeile 173)
"Unauthorized: Access denied for user admin"

Hope someone can shade a light on this...
Thanks in advance,
NR