My administration menu dissapears when installing a module I have created a module that implements hook_menu() using the following code:

function mypbm_menu() {
  $items['pbg'] = array(
    'title' =&gt; 'Theming example',
    'description' =&gt; 'Examples of implementing theme functions.',
    'page callback' =&gt; 'pbg',
    'access callback' =&gt; TRUE
  );
  return $items;
}

function pbg($id) {
  $stringit = $id;

  return $stringit;
}


The module works the way it is supposed to work; when it is turned on, the Administration menu module disappears.  

Does anyone know why?
The reason in my case was the character encoding of the "mymodule.module" file. 
Changing it back from "UTF-8" to "ANSI" solved the problem.