An unhandled error occured

Security exception - value of $_GET['SMPagesId'] = '3forsideold' is in conflict with value restriction 'Guid'

Stack trace
#0 /var/www/bodernehavn.dk/public_html/base/SMEnvironment.class.php(86): SMEnvironment::getValidatedValue('$_GET', Array, 'SMPagesId', 'Guid', Array)
#1 /var/www/bodernehavn.dk/public_html/extensions/SMPages/FrmViewer.class.php(32): SMEnvironment::GetQueryValue('SMPagesId', 'Guid')
#2 /var/www/bodernehavn.dk/public_html/extensions/SMPages/FrmViewer.class.php(271): SMPagesFrmViewer->loadPage()
#3 /var/www/bodernehavn.dk/public_html/extensions/SMPages/Main.class.php(124): SMPagesFrmViewer->Render()
#4 /var/www/bodernehavn.dk/public_html/base/SMController.class.php(193): SMPages->Render()
#5 /var/www/bodernehavn.dk/public_html/base/SMController.class.php(135): SMController->loadExtension('SMPages')
#6 /var/www/bodernehavn.dk/public_html/index.php(17): SMController->Execute()
#7 {main}