Missing edit tabs on only one content type
If you have a dsm($tabs) at the top of your page.tpl.php and it's showing it's set, nothing should be unsetting it by the time it is output later on in the template.

For example, in the default D6 page.tpl.php, it does this...

&lt;?php if (!empty($tabs)): ?&gt;&lt;div class="tabs"&gt;&lt;?php print $tabs; ?&gt;&lt;/div&gt;&lt;?php endif; ?&gt;


and in D7 it does this...

&lt;?php if ($tabs): ?&gt;&lt;div class="tabs"&gt;&lt;?php print render($tabs); ?&gt;&lt;/div&gt;&lt;?php endif; ?&gt;


...so, I'd take a look at the page source and see if css or something else is causing it to be hidden. For example, perhaps your theme is doing stuff like cascading a class in the body with the tabs class.