--- /buddypress/bp-core/bp-core-templatetags.php (BP 1.2.5.2)	Mon Jul 26 11:07:37 2010
+++ /buddypress/bp-core/bp-core-templatetags.php (working copy)	Mon Jul 26 11:03:03 2010
@@ -1517,7 +1517,14 @@
 }
 
 function bp_is_activity_front_page() {
-	return ( 'page' == get_option('show_on_front') && 'activity' == get_option('page_on_front') && $_SERVER['REQUEST_URI'] == bp_core_get_site_path() );
+	if ( bp_core_is_multisite() ) {
+		global $current_blog;	
+		$path = $current_blog->path;
+	}
+	else
+		$path = bp_core_get_site_path();
+
+	return ( 'page' == get_option('show_on_front') && 'activity' == get_option('page_on_front') && $_SERVER['REQUEST_URI'] == $path );
 }
 
 function bp_is_directory() {