Order ASC strange behaviour in a loop

I already posted this on stackoverflow.com:

https://stackoverflow.com/questions/15674015/wp-query-strange-behaviour-with-order-asc

If I set order to DESC it works ok, but with ASC I don’t get any images. Does this make sense to anyone?

This loop is happening inside my plugin. Shortcode is inserted in my home.php template inside a theme(Responsive theme).

Any help would be great since I’m a little stuck here… and just before launching the site.. ??