Right my fault, I just went with the first line the search engine brought back.

This is a different function (deletearticle) while the function I modified was deletepage below.

I might have missed something, that file you attached fixed the problem. I opened it to check the code.

You said replace...

$database -> dbquery( "DELETE FROM " . DB_PREFIX . "esselbach_ct_articlespages WHERE articlepage_article = '" . $options[ 1 ] . "'" );
$database -> dbquery( "DELETE FROM " . DB_PREFIX . "esselbach_ct_articlescomments WHERE articlecomment_article = '" . $options[ 1 ] . "'" );

With this...

$database -> dbquery( "DELETE FROM " . DB_PREFIX . "esselbach_ct_articlespages WHERE articlepage_id = '" . $options[ 1 ] . "'" );

But this was in the file you attached...

$database -> dbquery( "DELETE FROM " . DB_PREFIX . "esselbach_ct_articles WHERE article_id = '" . $options[ 1 ] . "'" );
$database -> dbquery( "DELETE FROM " . DB_PREFIX . "esselbach_ct_articlespages WHERE articlepage_article = '" . $options[ 1 ] . "'" );

This modification works fine on my test installation. Here my modified adminmanagearticles.php file.
   adminmanagearticles.zip

No it didn't work. I just tried creating a new article with a few pages.

In the Manage Articles section it says "3 pages".

Then I go in and delete a page and in the Manage Articles section it says "2 pages".

However if I go back into that article all 3 pages are still there.

This should fix this problem. Open /cadmin/articles/adminmanagearticles.php in an editor and replace:

          $database -> dbquery( "DELETE FROM " . DB_PREFIX . "esselbach_ct_articlespages WHERE articlepage_article = '" . $options[ 1 ] . "'" );

           $database -> dbquery( "DELETE FROM " . DB_PREFIX . "esselbach_ct_articlescomments WHERE articlecomment_article = '" . $options[ 1 ] . "'" );

with:

           $database -> dbquery( "DELETE FROM " . DB_PREFIX . "esselbach_ct_articlespages WHERE articlepage_id = '" . $options[ 1 ] . "'" );