Explicitly added driver name variable in each DB driver, based on this bug report: #4436
diff --git a/system/database/drivers/mssql/mssql_driver.php b/system/database/drivers/mssql/mssql_driver.php
index ed6eadb..02b975a 100644
--- a/system/database/drivers/mssql/mssql_driver.php
+++ b/system/database/drivers/mssql/mssql_driver.php
@@ -37,7 +37,8 @@
 	 */

 	var $_count_string = "SELECT COUNT(*) AS ";

 	var $_random_keyword = ' ASC'; // not currently supported

-	

+	var $dbdriver		= 'mssql';

+

 	/**

 	 * Non-persistent database connection

 	 *