Today I had an interesting experience... all of a sudden, all the blocks of a given theme disappeared.

It has been working just fine for months, so I really wasn't sure what the heck it could be.

The fact was that the theme was called the same as the module (as I work for a given client, I tend to do that...)

At some point, I must have added a function with a specific name and that would influence the theme. The result being blocks going bye bye!

I checked and the block content is computed just fine, the problem is the theme('block', $block) call. Although the $block->content is the HTML of the block as expected, the theme() call returns an empty string and that for all the blocks and the result is a Drupal site without any blocks.

There is the function that generates the HTML for all the blocks in a given region:

function theme_blocks($region) {
  $output = '';

  if ($list = block_list($region)) {
    foreach ($list as $key => $block) {
      // $key == <i>module</i>_<i>delta</i>
      $output .= theme('block', $block);
    }
  }

  // Add any content assigned to this region through drupal_set_content() calls.
  $output .= drupal_get_content($region);

  return $output;
}

As you can see, it will theme() the blocks. I'm still not too sure what happened, although I noticed that having the module function with name_settings() would create a form in the theme settings too. Ooops!

Anyway, renaming the theme fixed that problem. Now we may find a few other problems as I used that path quite a bit (I kept a softlink for images, etc., but there could be other things that break down...)