[support] Error with my first module

[Marolijo]

Hello, I'm tryin' to setup my first module. Created the .info and
.module files on sites/all/modules/modulename, and start with a very
basic block but when I enable th emodule it breaks my primary links
menu (superfish menu).

Here's the simple code on .module , any idea?

Wich is the simplest way to debug this kind of problems?

Thank's for your time an patience.

<?php
function modulename_block($op='list',$delta=array(),$edit=array())
{
      switch ($op)
     {

        case 'list':
                       $blocks[0]['info'] = t('module test');
                       return $blocks;
                       break;
         case 'view':


          $content = 'hello world';
          $blocks['subject'] = t('module test');
          $blocks['content'] = "Test";
       return $blocks;
       break;
      }
}