.NET 2.0 Web App Authentication Failing: “The ticket supplied was invalid”

Question

I have a .NET 4.0 application with a 2.0 application as a child. The web applications are not in a multi-server environment; only one server is involved in serving these reques

Answer 1

There is also one more cause of this problem. Even on the same machine, same IIS and same .NET framework if one of your applications has

then sharing authentication cookie will not work.

Removing requestValidationMode solves the problem. But sometimes you cannot do it and it needs to stay there. I'm yet to discover what to do in such situation