Problem with Interface Translation

Hello,

I am trying to translate my site internetinesparduotuves.eu to Lithuanian
I imported .po file and most of records are translated
Lithuanian 3989/6817 (58.52%) 3989/3989 (100%) 3989/3989 (100%) 3989/4043 (98.66%) 3989/3993 (99.9%) 3989/4013 (99.4%)

However almost all user site is still in English.
I go to path
Home » Administration » Configuration » Regional and language » Translate interface
and got many many errors here:
Notice: Undefined index: field in _locale_translate_seek() (line 1931 of /home/fxanalysis/domains/internetinesparduotuves.eu/public_html/includes/locale.inc).

I went to locale.inc file line 1931(this line in bold)

$rows = array();
foreach ($strings as $lid => $string) {
$rows[] = array(
$groups[$string['group']],
array('data' => check_plain(truncate_utf8($string['source'], 150, FALSE, TRUE)) . '
' . $string['location'] . ''),
$string['context'],
array('data' => _locale_translate_language_list($string['languages'], $limit_language), 'align' => 'center'),
array('data' => l(t('edit'), "admin/config/regional/translate/edit/$lid", array('query' => drupal_get_destination())), 'class' => array('nowrap')),
array('data' => l(t('delete'), "admin/config/regional/translate/delete/$lid", array('query' => drupal_get_destination())), 'class' => array('nowrap')),
);
}

And below there are many errors:
Built-in interface An AJAX HTTP error occurred.
; misc/drupal.js lt edit delete
Built-in interface HTTP Result Code: !status
; misc/drupal.js lt edit delete
Built-in interface An AJAX HTTP request terminated abnormally.
; misc/drupal.js lt edit delete
Built-in interface Debugging information follows.
; misc/drupal.js

and much more.

What needs to be done to solve this problem ?
Could site be fixed or needs to be done from beginning ?
Any suggestions ?

Happy New Year !

Edward