Have you searched the http://laravel.io/forum?tags=authentication,security section, there are several posts
where folks had similar problems and were solved. Are you using L4 or L5? Have you tried models just to verify it would work there? Have you dumped your autoloads, have you tried

 use Snippet\User;

Did you check namespacing for Snippet, making it exactly like models is setup? etc etc etc.

Im using 4.2.* Laravel. I get my error here: /var/www/snippet/vendor/laravel/framework/src/Illuminate/Auth/EloquentUserProvider.php

         *
	 * @return \Illuminate\Database\Eloquent\Model
	 */
	public function createModel()
	{       
		$class = '\\'.ltrim($this->model, '\\');
 
		return new $class; //\Snippet\User
	}

but if i put \Snippet\User instead $class everything is fine.

Having the same problem right now, any updates on a solution?

UPDATE:

Have you tried to change the "model" in you auth.php config to Snippet\User ?

'model' => 'Snippet\User',

Can you please post the complete error?