I would like upgrade a site (Drupal 6 -> Drupal 7)

Server parameter: PostgreSQL 9.1, PHP 5.3.10 and Apache 2.2.22

The source site is Drupal 6.26 with i18n 6.x-1.10 module. Target is Drupal 7.19, i18n 7.x-1.8 and Variable 7.x-2.2. The site have two languages ad primary language is English.

But If enable i18n_string module, the update function ran is fatal error:

$ drush en -y i18n_string
The following extensions will be enabled: i18n_string
Do you really want to continue? (y/n): y
WD php: PDOException: SQLSTATE[42703]: Undefined column: 7 ERROR: column "s" of relation "drupal_i18n_string" does not exist [error]
LINE 1: UPDATE drupal_i18n_string s SET s.textgroup = (SELECT l.text...
^: UPDATE {i18n_string} s SET s.textgroup = (SELECT l.textgroup FROM {locales_source} l
WHERE l.lid = s.lid); Array
(
)
in i18n_string_update_7000() (line 217 of
/var/www/sites/all/modules/contrib/i18n/i18n_string/i18n_string.install).
PDOException: SQLSTATE[42703]: Undefined column: 7 ERROR: column "s" of relation "drupal_i18n_string" does not exist
LINE 1: UPDATE drupal_i18n_string s SET s.textgroup = (SELECT l.text...
^: UPDATE {i18n_string} s SET s.textgroup = (SELECT l.textgroup FROM {locales_source} l WHERE l.lid = s.lid); Array
(
)
in i18n_string_update_7000() (line 217 of /var/www/sites/all/modules/contrib/i18n/i18n_string/i18n_string.install).
Drush command terminated abnormally due to an unrecoverable error. [error]