Index: kernel/application.php
===================================================================
--- kernel/application.php	(revision 12677)
+++ kernel/application.php	(working copy)
@@ -533,22 +533,26 @@
 		return $path;
 	}
 
-	function GetDefaultLanguageId()
+	function GetDefaultLanguageId($init = false)
 	{
-		static $language_id = 0;
+		static $language_info = Array ();
 
-		if ($language_id > 0) {
-			return $language_id;
+		$language_key = ($this->IsAdmin() && $init) || (count($language_info) == 1) ? 'Admin' : 'Front';
+
+		if (array_key_exists($language_key, $language_info) && $language_info[$language_key] > 0) {
+			return $language_info[$language_key];
 		}
 
 		$table = $this->getUnitOption('lang', 'TableName');
 		$id_field = $this->getUnitOption('lang', 'IDField');
 
-		$sql = 'SELECT '.$id_field.'
+		$sql = 'SELECT '.$id_field.', IF(AdminInterfaceLang, "Admin", "Front") AS LanguageKey
 				FROM '.$table.'
-				WHERE (PrimaryLang = 1) AND (Enabled = 1)';
-		$language_id = $this->Conn->GetOne($sql);
+				WHERE (AdminInterfaceLang = 1 OR PrimaryLang = 1) AND (Enabled = 1)';
+		$language_info = $this->Conn->GetCol($sql, 'LanguageKey');
 
+		$language_id = $language_info && array_key_exists($language_key, $language_info) ? $language_info[$language_key] : false;
+
 		if (!$language_id && defined('IS_INSTALL') && IS_INSTALL) {
 			$language_id = 1;
 		}
Index: kernel/languages/phrases_cache.php
===================================================================
--- kernel/languages/phrases_cache.php	(revision 12677)
+++ kernel/languages/phrases_cache.php	(working copy)
@@ -109,12 +109,7 @@
 		}
 		else {
 			if ($this->Application->IsAdmin()) {
-				$id_field = $this->Application->getUnitOption('lang', 'IDField');
-				$table_name = $this->Application->getUnitOption('lang', 'TableName');
-				$sql = 'SELECT '.$id_field.'
-						FROM '.$table_name.'
-						WHERE AdminInterfaceLang = 1';
-				$this->LanguageId = $this->Conn->GetOne($sql);
+				$this->LanguageId = $this->Application->Session->GetField('Language');
 			}
 			else {
 				$this->LanguageId = $this->Application->GetVar('m_lang');
Index: kernel/session/inp_session.php
===================================================================
--- kernel/session/inp_session.php	(revision 12677)
+++ kernel/session/inp_session.php	(working copy)
@@ -115,7 +115,7 @@
 	{
 		$fields_hash = Array (
 			'PortalUserId'	=>	$this->Application->IsAdmin() ? 0 : -2, // Guest
-			'Language'		=>	$this->Application->GetDefaultLanguageId(),
+			'Language'		=>	$this->Application->GetDefaultLanguageId(true),
 			'Theme'			=>	$this->Application->GetDefaultThemeId(),
 			'IpAddress'		=>	$_SERVER['REMOTE_ADDR'], // getenv('REMOTE_ADDR') won't work on IIS, so use $_SERVER instead
 			'GroupId'		=>	$this->Application->ConfigValue('User_GuestGroup'),