There is something strange on the server:
This causes error 500:
ob_start();
phpinfo(INFO_MODULES);
$modules = ob_get_contents();
ob_end_clean();
Because phpinfo() crashes the server:
http://arume.com.es/galeria/iv-includes/phpinfo.php
You can notice that the page breaks in the middle. Compare to this:
https://www.photo.gallery/demo/x2/iv-includes/phpinfo.php
This might be caused by using CGI as PHP API or maybe IonCube affects it somehow.
We've commented this line out in /iv-includes/common.inc.php:140 and it works, but you might get other issues. Try to contact your server support and see if they can fix this.
If there won't be any resolution, I would recommend you to change hosting.