=== modified file 'modules/block/block.module'
--- modules/block/block.module	2010-04-10 11:11:46 +0000
+++ modules/block/block.module	2010-04-13 16:26:34 +0000
@@ -349,6 +349,10 @@
             // value if the module did not.
             $block['pages']  = '';
           }
+          // Set region to default if not specified.
+          if (!isset($block['region'])) {
+            $block['region'] = key($regions);
+          }
           // Add defaults and save it into the database.
           drupal_write_record('block', $block);
           // Set region to none if not enabled.
@@ -913,3 +917,12 @@
     ->condition('module', $modules, 'IN')
     ->execute();
 }
+
+/**
+ * Implements hook_modules_enabled().
+ *
+ * Add modules' blocks to the database in case they are set active by default.
+ */
+function block_moudles_enabled($modules) {
+  _block_rehash();
+}