Android Sqlite update row wont work in Custom Dialog

I've created a class myDialog extends Dialog and in this class I create an instance of my class DBHelper that extends SQLiteOpenHelper In other activity insert, delete and update record work normally but in class myDialog only insert and delete work, update fails. Why? The only thing that changes between the call of the class activity to this dialog is: in other activity like Main or Info db = new DBHelper(this); in class myDialog DB1 = new DBHelper(getContext());

The logcat reporting this while call update in myDialog 09-12 19:06:48.272: W/FileUtils(2444): Failed to chmod(/data/data/com.dan.client/databases/messaggi.db): libcore.io.ErrnoException: chmod failed: EPERM (Operation not permitted)

I repeat and confirm that all other activity I also work out the update as one would expect. Thank you in advance