Index: wp-includes/ms-functions.php
===================================================================
--- wp-includes/ms-functions.php	(revision 30972)
+++ wp-includes/ms-functions.php	(working copy)
@@ -1815,7 +1815,12 @@
 		if ( get_option( 'default_category' ) == $term_id )
 			update_option( 'default_category', $global_id );
 
-		$wpdb->update( $wpdb->terms, array('term_id' => $global_id), array('term_id' => $term_id) );
+		$replacement_term = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $wpdb->terms WHERE term_id = %d", $term_id ), ARRAY_A );
+
+		$wpdb->delete( $wpdb->terms, array('term_id' => $replacement_term['term_id'] ) );
+		$replacement_term['term_id'] = $global_id;
+		$wpdb->insert( $wpdb->terms, $replacement_term );
+
 		$wpdb->update( $wpdb->term_taxonomy, array('term_id' => $global_id), array('term_id' => $term_id) );
 		$wpdb->update( $wpdb->term_taxonomy, array('parent' => $global_id), array('parent' => $term_id) );