Prestashop 1.6 : theme columns not visible on cms page

My client had the following problem : the left column was not visible on any CMS pages in his Prestashop 1.6 installation. Furthermore, the cms meta did not show up in the theme configuration page. Here's how you can manually set the column visibility:

Go to your Prestashop database in PhpMyAdmin. Then execute the following query (I'm assuming table prefix ps_ here..substitute if you are using a different prefix)

UPDATE ps_theme_meta SET left_column = 1 WHERE id_meta = 
(SELECT id_meta from ps_meta WHERE page = "cms")

This of course also works for the right column (substitute left_column with right_column in the query), or with any other page type found in the ps_meta table.