while using spsecurity.runwithelevatedprivileges if we want to create or update a splistitem using the elevated previledges, we need to create new SPSite and SPWeb objects, but you would get an error “The security validation for this page is invalid …” since a new SPContext object is created.

 

There are two ways to get past this error

1) set SPWeb.AllowUnsafeUpdates = true

    http://moldenco.blogspot.co.uk/2007/05/spsecurityrunwithelevatedprivileges-to.html

http://social.msdn.microsoft.com/forums/en-US/sharepointdevelopment/thread/63106621-cbde-44d9-b3cf-07bddc0856f1/

2) Use SPUtility.ValidateFormDigest()

http://dbremes.wordpress.com/2010/07/21/runwithelevatedprivileges-and-error-the-security-validation-for-this-page-is-invalid/