Hi Cuneyt,
Oh, I am sorry -- I forgot to tell that first the content of two tables should be manually deleted and I also forgot a code line -- I did it when the version 2.3.0 was published so I forgot all the details -- sorry!

Thus, here once again, from the beginning:
Did you customize some email templates? They will be lost if you follow this description, thus remember or copy the changes you did.
Is there a possibility for you to first test all this on a testing system? I've just tested it on my testing system, but...
I've just checked the count of the default emails in the version 2.3.1-2: There are 64 in English and 50 in Turkish (s. locale/en_US/emailTemplates.xml vs. locale/tr_TR/emailTemplates.xml
In order to get a clean new installation the following steps are necessary:
Reset your email customization: Go to the 'Prepared Email' page and click on 'Reset All Templates' -- this will delete all your changes/email text customization.
Then you should delete the content of the tables 'email_templates_default' and 'email_templates_default_data' in your database like this:
DELETE FROM email_templates_default;
DELETE FROM email_templates_default_data;
After this, there are no email templates in your system.
Use this new script like explained in the last posting to install the email templates:
<?php
require(dirname(__FILE__) . '/bootstrap.inc.php');
// Install email template list and data for each locale
$emailTemplateDao =& DAORegistry::getDAO('EmailTemplateDAO');
// comment the next line when changing the locale!!!:
$emailTemplateDao->installEmailTemplates($emailTemplateDao->getMainEmailTemplatesFilename());
$emailTemplateDao->installEmailTemplateData($emailTemplateDao->getMainEmailTemplateDataFilename('en_US'));
?>
The script changed a little bit:
The first line changed -- it changed for the version 2.3.1-2.
The following line (that installs the content for the table 'email_templates_default') is new:
$emailTemplateDao->installEmailTemplates($emailTemplateDao->getMainEmailTemplatesFilename());
This should be done just once, so please don't forget to remove or comment (putting '//' in front of it) this line when you change the locale!!!
I hope it will work and you will have a clean new installation of the default email templates -- you should then have 64 emails in English and 50 in Turkisch. Then you can make changes if necessary.
Best regards