After a couple of days that the patch supee-7405 was released I've decided to install the it.
I did a backup of my website because I could see there were a lot of files to modify and I suspected that something could be wrong and yes, something has been wrong.
When I am on the admin panel and I go to sales>orders it looks like everything is ok. But when I try to access to any of those orders I can't see the information of that order.

Does this have a solution or I should go back to my backup?
var/report. But where can I see such non-critical error information? – aleixrav Feb 26 '16 at 11:01var/logfor Magento logs. To get your server error logs, you can do it via cPanel or an other server admin web access. If you have full access to your server via SSH you can find them in the/var/logfolder – Raphael at Digital Pianism Feb 26 '16 at 11:02var/log/system.log. The problem is the file weights 20GB and it would take a lot of time to download it. – aleixrav Feb 26 '16 at 11:06supee-7405 version-1.1. Thank you very much for your help anyway. – aleixrav Feb 26 '16 at 11:39