Custom Post Type And “fopen”

Never posted here but since I can’t find a solution on my own, let’s abuse your kindness!

I’m adding some custom post types through my theme.

The first custom type works like a charm, but as soon as I add the second (and third) one, the apache’s error log reports a PHP Warning when trying to do a search action (like the one to search a post to attach a media).

fopen(http://localhost/site/wp-cron.php?doing_wp_cron) [<a href='function.fopen'>function.fopen</a>]: failed to open stream [...] in E:\www\site\wp-includes\class-http.php on line 876, referer: http://localhost/raw/wp-admin/edit.php

It only happens when I set the ‘thumbnail’ string into the $args[‘supports’] array passed to the register_post_type function.

Any help would be much appreciated!

Regards