Problem with "foreign" (swedish) characters in a custom module

I'm writing an own module for my site. Unfortunately I'm Swedish and need to use some weird ("foreign") letters called Å, Ä and Ö in some places. For example in hook_menu (outputting the menu name).

My problem is that these letters doesn't display properly at all. Instead they are substituted with a square or a Chinese character (depending on browser).

I know Drupal can handle these characters. It does so in all types of content, and so on. But apparently not in my own modules...

What am I doing wrong?

Here's a code example from hook_menu:

function sdtabla_menu() {

  $items = array();

  $items[] = array(
    'path' => 'tabla',
    'title' => t('Tablå'),
    'callback' => 'sdtabla_visa',
    'access' => user_access('Visa tablå'),
    'type' => MENU_NORMAL_ITEM,
  );

  return $items;
}

Grateful for any help!