The security validation for this page is invalid. Click Back in your Web

If you are getting the following error, while renaming the page title using publishingpage object
"The security validation for this page is invalid. Click Back in your Webbrowser, refresh the page, and try your operation again."

Code Snippet:

PublishingWeb publishingweb = PublishingWeb.GetPublishingWeb(newUri("http://YourPortal/Plans/"));
PublishingPage pp =publishingweb.GetPublishingPages()["Pages/TestArticle.aspx"];
pp.Title = e.Node.Text;
pp.Update();

You should check for this :

Navigate thru the followwing and turn the security validation Off

Central Administration--->application management---->web application settings-->"turn security validation off"