Hello, thank you very much for your answers. I had already installed the 1.5.3 version, and still keeps happening anyway as helped me find the file that stores the variable. So now I have to work for.
For now I have changed the permissions of / cdata / conf.php to 545, have if I was not so far removed from. Keep working on the issue. Thank you again.

Forgive for my English
Additional fields disappear, I think an additional field then use in my news, but every 2 or 3 days is deleted, and I have to recreate it. I'm no expert in PHP and is no longer how to solve it.
A greeting and thank you very much.