diff -urp privatemsg_limits/privatemsg_limits.module privatemsg_limits_patched/privatemsg_limits.module
--- privatemsg_limits/privatemsg_limits.module	2011-02-25 02:11:26.000000000 +0000
+++ privatemsg_limits_patched/privatemsg_limits.module	2011-02-25 20:35:26.000000000 +0000
@@ -16,7 +16,7 @@ function privatemsg_limits_form_privatem
     privatemsg_limits_warning();
   }
   //add the additional validate function to the privatemsg_new form.
-  $form['#validate'][] = 'privatemsg_limits_form_privatemsg_new_validate';
+  $form['privatemsg']['submit']['#validate'][] = 'privatemsg_limits_form_privatemsg_new_validate';
 }
 
 /**