ASP.NET MVC Anti Forgery Token - Apps in same IIS Server

Question

I have more than one app running in a IIS and I get the following error:

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 configuration specifies explicit encryption and validation keys.

That occurs when I open a web app, for example http://localhost:90 and logging into it. Later, I open a second tab (http://localhost:91) and logging into the web app. After that, I return to the first tab and press Log Off (or any other post to any other form) and I get the error.

• There isn't more than one AntiForgeryToken in the same views
• I tried to configure individual MachineKeys in the web apps and I couldn't resolve it (from the IIS and from the web.config too).