Mailing stopped working after CiviCRM, PHP and Drupal upgrade
The issue was affecting multilingual installations.
If the multilingual support is turned off in the settings everything works. 

Applying the fix solves the problem for multilingual installations.

You can see the @monishdeb's fix on github, the fix will be included in the next version.

And here's the patchfile I used

131c131
&lt;              -&gt;where('mailing_id = #mailing_id AND entity_table IN ("!groupTableName", "civicrm_mailing")')
---
&gt;              -&gt;where('mailing_id = #mailing_id AND entity_table IN ("civicrm_group", "civicrm_mailing")')
133d132
&lt;              -&gt;param('!groupTableName', CRM_Contact_BAO_Group::getTableName())