Index: includes/common.inc
===================================================================
--- includes/common.inc	Wed Apr 28 14:29:35 2010
+++ includes/common.inc	Wed Apr 28 14:28:58 2010
@@ -3424,7 +3424,7 @@
     }
 
     // For inserts, populate defaults from Schema if not already provided
-    if (!isset($object->$field) && !count($update) && isset($info['default']) && !array_key_exists($field, $object)) {
+    if (!isset($object->$field) && !count($update) && isset($info['default'])) {
       $object->$field = $info['default'];
     }
 
@@ -3446,10 +3446,6 @@
       else {
         $values[] = serialize($object->$field);
       }
-    }
-    elseif (empty($info['not null']) && array_key_exists($field, $object) && count($update)) {
-      $fields[] = $field;
-      $placeholders[] = 'NULL';
     }
   }