Index: bp-core/bp-core-activation.php
===================================================================
--- bp-core/bp-core-activation.php	(revision 2317)
+++ bp-core/bp-core-activation.php	(working copy)
@@ -7,7 +7,7 @@
 		return false;
 
 	/* Check if an activation key has been passed */
-	if ( isset( $_GET['key'] ) ) {
+	if ( isset( $_GET['key'] ) && $wpdb->blogid == BP_ROOT_BLOG ) {
 
 		require_once( ABSPATH . WPINC . '/registration.php' );