Index: modules/system/system.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.install,v
retrieving revision 1.174
diff -u -r1.174 system.install
--- modules/system/system.install	11 Nov 2007 06:56:44 -0000	1.174
+++ modules/system/system.install	11 Nov 2007 18:39:07 -0000
@@ -4466,6 +4466,15 @@
 }
 
 /**
+ * Create consistent empty region for disabled blocks.
+ */
+function system_update_6036() {
+  $ret = array();
+  $ret[] = update_sql("UPDATE {blocks} SET region = '' WHERE status = 0");
+  return $ret;
+}
+
+/**
  * @} End of "defgroup updates-5.x-to-6.x"
  * The next series of updates should start at 7000.
  */
Index: modules/block/block.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/block.install,v
retrieving revision 1.6
diff -u -r1.6 block.install
--- modules/block/block.install	6 Nov 2007 11:40:15 -0000	1.6
+++ modules/block/block.install	11 Nov 2007 18:39:05 -0000
@@ -52,7 +52,7 @@
         'type' => 'varchar',
         'length' => 64,
         'not null' => TRUE,
-        'default' => 'left',
+        'default' => '',
         'description' => t('Theme region within which the block is set.'),
       ),
       'custom' => array(