Gulp error: [Error: no writecb in Transform class]

Hi there

I am doing a fresh install of Laravel and Spark. I've followed the Installation instructions and everything went quite well other than when I run gulp I get the following error:

luke@DC1:~/islive$ gulp
[04:52:45] Using gulpfile ~/islive/gulpfile.js
[04:52:45] Starting 'all'...
[04:52:45] Starting 'less'...
[Error: no writecb in Transform class]

My gulpfile.js is:

var elixir = require('laravel-elixir');

/*
 |--------------------------------------------------------------------------
 | Elixir Asset Management
 |--------------------------------------------------------------------------
 |
 | Elixir provides a clean, fluent API for defining some basic Gulp tasks
 | for your Laravel application. By default, we are compiling the Sass
 | file for our application, as well as publishing vendor resources.
 |
 */

elixir(function(mix) {
    mix.less('app.less')
       .browserify('app.js', null, null, { paths: 'vendor/laravel/spark/resources/assets/js' })
       .copy('node_modules/sweetalert/dist/sweetalert.min.js', 'public/js/sweetalert.min.js')
       .copy('node_modules/sweetalert/dist/sweetalert.css', 'public/css/sweetalert.css');
});

My versions:

node -v: v0.10.25
npm -v: 1.3.10
gulp -v: CLI version 3.9.1, Local version 3.9.1

In the Dev Tools console it tells me that public/js/sweetalert.min.js and public/css/sweetalert.css cannot be found. It appears they have not been copied into the public directory. I have a feeling it is an issue with the gulpfile.js as I am running another laravel installation on the same server in another directory without any issues.

Has anyone else experienced a similar issue?

Many thanks for any input! Luke