Problem with automatic warnings from posts

[CORSO]

We are using AWS 3.6.1 runing on Vbulletin 3.6.5

Warning from pms are working correctly but when obscene words are used in posts, they are censored but no warning issued

The error we have is

Database error in vBulletin 3.6.5:

Invalid SQL:

INSERT INTO pmtext_warned
(fromuserid, fromusername, title, before_title, message, before_message, touserarray, dateline)
VALUES
(,
'',
'Re: uno dos uno dos probando.',
'Re: uno dos uno dos probando.',
'',
'<i><u>arj25</u></i>',
'',
1176631959);

MySQL Error : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '
'',
'Re: uno dos uno dos probando.',
'Re: uno dos uno dos probando.' at line 4
Error Number : 1064


where arj25 is the Obscene Word used for tests

The same message sent in a pm, works correctly

Any suggestion?