Revert back some escape_identifiers() to proect_identifiers() as the first one can't handle arrays
diff --git a/system/database/drivers/mysqli/mysqli_forge.php b/system/database/drivers/mysqli/mysqli_forge.php
index a1f58f0..e0e98f1 100644
--- a/system/database/drivers/mysqli/mysqli_forge.php
+++ b/system/database/drivers/mysqli/mysqli_forge.php
@@ -62,7 +62,7 @@
 
 				$sql .= "\n\t".$this->db->escape_identifiers($field);
 
-				empty($attributes['NAME']) OR $sql .= ' '.$this->db->protect_identifiers($attributes['NAME']).' ';
+				empty($attributes['NAME']) OR $sql .= ' '.$this->db->escape_identifiers($attributes['NAME']).' ';
 
 				if ( ! empty($attributes['TYPE']))
 				{
@@ -152,7 +152,7 @@
 				if (is_array($key))
 				{
 					$key_name = $this->db->escape_identifiers(implode('_', $key));
-					$key = $this->db->escape_identifiers($key);
+					$key = $this->db->protect_identifiers($key);
 				}
 				else
 				{