Visual Webpart redirects to 'Web page has expired. click Refresh button to load..."

Hi

I have a custom visual webpart for uploading  files and added the webpart to Documentlibrary/Forms/Allitems.aspx. The documentlibrary has multiple nested subfolders and files in it.  Everytime when I hit Internet explorer ‘Back’ button(browser back) it expires the page.

I have tried so far below suggestions but none of those helped me to resolve.

http://support.microsoft.com/kb/888828/en-us

http://blogs.msdn.com/b/navdeepm/archive/2010/04/29/microsoft-sharepoint-spexception-the-security-validation-for-this-page-is-invalid-in-sharepoint-2010.aspx

http://go4answers.webhost4life.com/Example/prevent-browser-proxy-caching-web-pages-83941.aspx

I have noticed when I delete the webpart from the document library, the browser back button works fine. I thought I have to add some cache script on my webpart but the ‘Back’ button works great in Google chrome. No issues even in Safari.

Will you please help to overcome this page expiry?

Thanks

Shri