How to add new blocks when "The block X was assigned to the invalid region Y and has been disabled" I have inherited a site (in Drupal 6) and the original developers are completely out of the picture. I need to add a block but it looks like they've customized things and blocks are being rendered in a way other than assigning them to block regions as per the default.

I get a lot of warnings to the effect of The block X was assigned to the invalid region Y and has been disabled but those blocks still appear on the site. So they must be being brought in another way. I am not too terribly worried about the warnings (so seeing this discussion is not really what I need: https://drupal.org/node/1172560). I am more concerned that it is taking me hours to add a link and image to the homepage.

I see that the previous developers installed the Nodeblock and Nodeblock Auto modules and the nodes that come in have html ids like: block-nodeblockauto-node_&lt;NID&gt; so I imagine this is how they are being brought in. 

But I don't see any options in the admin panel for configuring nodes any further than what I am used to from the default. In looking through the template files for the custom theme, I also do not see where these are being brought in.

Note: I am not in a position to migrate to Drupal 7 so I have to keep things in Drupal 6 for now.
In D7 I finally got rid of that message by placing an if ($theme == variable_get('theme_default', '0')) around the region assignment. So the block only gets assigned to my (default) frontend theme which actually contains the region the block is assigned to.

function MYMODULE_block_info_alter(&amp;$blocks, $theme, $code_blocks) {
  if ($theme == variable_get('theme_default', '0')) {
        if (isset($blocks['MYMODULE']['MYMODULE_block'])) {
            $blocks['MYMODULE']['MYMODULE_block']['status'] = 1;
            $blocks['MYMODULE']['MYMODULE_block']['region'] = 'header';
            $blocks['MYMODULE']['MYMODULE_block']['weight'] = 2;
            $blocks['MYMODULE']['MYMODULE_block']['visibility'] = BLOCK_VISIBILITY_NOTLISTED;
        }
    }
}