lists.asmx updatelistitems the security validation for this page is invalid Posted on November 17, 2010February 18, 2015 by Iain 'Cutty' Carlin And the answer was here: http://weblogs.asp.net/jan/archive/2009/05/25/quot-the-security-validation-for-this-page-is-invalid-quot-when-calling-the-sharepoint-web-services.aspx ListSharePoint