We had a small problem with blank pages every time we tried to update something from admin panel.
I have tried in vain to find a solution on Prestashop. After i have tried all the non-sense solutions from the forum, i have decided to do it by myself. So i have opened the error.log from the server, i havent tryed debug mode. I had this message> Warning: Cannot modify header information - headers already sent by..admin line1 etc
So i looked around in admin.php from translations and i have noticed that it was modified, so i have just copied backed admin.php and the problem was fixed.
All the best from Bucharest..