Block wrapping DIV disable with theme hook?
You can specify an additional variable in hook_preprocess_block() and check for that variable in block.tpl.php file, example: 

function front_preprocess_block(&amp;$vars, $hook) {
  //dpm($vars);
  $vars['must_be_removed'] = FALSE;
  if(/* CONDITION e.g. $vars['elements']['#block']-&gt;delta == 'MY_BLOCK_DELTA' */) {
    $vars['must_be_removed'] = TRUE;
  }
}


and block.tpl.php file;

&lt;?php if($must_be_removed): ?&gt;
  &lt;?php print $content ?&gt;
&lt;?php else: ?&gt;
&lt;div id="&lt;?php print $block_html_id; ?&gt;" class="&lt;?php print $classes; ?&gt;"&lt;?php print $attributes; ?&gt;&gt;

  &lt;?php print render($title_prefix); ?&gt;
&lt;?php if ($block-&gt;subject): ?&gt;
  &lt;h2&lt;?php print $title_attributes; ?&gt;&gt;&lt;span&gt;&lt;?php print $block-&gt;subject ?&gt;&lt;/span&gt;&lt;/h2&gt;
&lt;?php endif;?&gt;
  &lt;?php print render($title_suffix); ?&gt;

  &lt;div class="content"&lt;?php print $content_attributes; ?&gt;&gt;
    &lt;?php print $content ?&gt;
  &lt;/div&gt;
&lt;/div&gt;
&lt;?php endif; ?&gt;