2
Solved.
This was the error:
Fatal error: Call to a member function on a non-object in /var/www/kernel/notification.php on line 99
Notice [PHP]: Undefined index: nosmiley in file modules/newbb/post.php line 166
Notice [PHP]: Undefined index: icon in file modules/newbb/post.php line 167
and white page after submitting new post.
I discovered that if someone who has notifications active deletes his own account directly from "View Account", the system dosn't delete all account rows from table ????_xoopsnotifications.
At least in 2.0.5 version.
I had to delete manually all rows from the table and re-enable all notifications from administration menu.
Does someone know if it is a bug of 2.0.5 version ?