--- views/plugins/signup_plugin_access_user_signup_list.inc.orig	2011-04-12 16:16:06.000000000 -0400
+++ views/plugins/signup_plugin_access_user_signup_list.inc	2011-04-12 16:16:29.000000000 -0400
@@ -22,7 +22,7 @@ class signup_plugin_access_user_signup_l
     $this->view->init_handlers();
     $user_arg = $this->options['signup_user_argument'];
     $argument = $this->view->argument[$user_arg];
-    return $account->uid == $argument->get_value();
+    return (is_object($argument)) && ($account->uid == $argument->get_value());
   }
 
   function get_access_callback() {
--- signup.module.orig	2011-04-12 16:14:55.000000000 -0400
+++ signup.module	2011-04-12 16:18:14.000000000 -0400
@@ -1723,7 +1723,7 @@ function signup_view_user_list_access($v
     $i++;
   }
 
-  return $user->uid == $view->argument[$argument_name]->get_value();
+  return (is_object($view->argument[$argument_name])) && ($user->uid == $view->argument[$argument_name]->get_value());
 }
 
 /**