title: Prestashop categories pages load very slow
body: <p>I have a prestashop v1.5.6 installed over PHP v5.3.10 on MySQL v5.5.35. The products and categories has been imported directly to the database.
  The categories module runs sometimes very slow. The web almost have no traffic. (<a href="http://tintaadomicilio.es" rel="nofollow">http://tintaadomicilio.es</a>)</p>
  
  <p>I have check the integrity of all categories in database. The left and night fields seems to be fine. Also, there are not categories without parent.
  I have check querys, mysql variables, cache, etc...
  There are no prestashop query in mysql-slow.log
  Also, the php5.log log do not contains any relevant information.</p>
  
  <p>I don't know what to do. My server is a dedicated one, i manage it personally. It have a optimal performance, other webs runs fine. I migrate recently to a new one (ubuntu 12.04 LTS), for other reasons, but in the old server happened the same.
  The categories (even the page that show the final product) runs slow some clicks, extremely slow other clicks, and sometimes runs fine. Its happens randomly.</p>
  
  <p>I need help.</p>