The anti-forgery token could not be decrypted. If this application is hosted by a Web Farm or cluster, ensure that all machines are running the same version of ASP.NET Web Pages and that the <machineKey> configuration specifies explicit encryption and validation keys. AutoGenerate cannot be used in a cluster.

The page produced by us contains an id (anitforgerytoken) - this is new each time.

It is generated from the a key value on the server (machineKey).

If you have a webfarm (more than one frontend) this key value on the server should be the same for all servers.

When ASP.NET gets a postback from a page with an antiforgerytoken it tries to verify it.

The goal is to avoid someone taking an old page and re-post multiple times.

If you wait really long from page gen to postback the token may expire.