[Moo] Getting error when making an ajax call

[websam]

I try to do this :

function deleteRole(roleId) {
    var req = Request({
        method: 'post',
        url: '/Role/Delete/' + roleId
    });
    req.send();
}

But get this error in firefox 3

    uncaught exception: Security error (NS_ERROR_DOM_SECURITY_ERR)

The web application is an asp.net mvc app.