I am very confused recently on a strange problem after you upgrade the sp 2007 to sp 2010. 1 . After upgrading the sp 2007 to sp 2010. 2. Deploy the solution package to the sp 2010 and a specified applicaiton. 3. Check features are successfully deployed. 4 --1 When you create a webpart page, then it appears the error below The security validation for this page is invalid. Click Back in your Web browser, refresh the page, and try your operation again. --2 When you create a publishing page, it is ok. But when you edit the page, you cannot add a webpart "Add a webpart link" is unclickable that's to say when you click it no reponse. Anyone who has ideas? Is it related to the site template?

Hey bafosh, Can you please go to the properties of the solution and change the framework that suits to your current version hope it may be 3.5 i think. Build the solution and deploy and activate. Try this and let me know is this solved your problem Thanks, Nivas