ASP.NET Forms Authentication failed for the request. Reason: The ticket supplied has expired

Question

I am getting this error many times in the event log and users are logged out.

Event code: 4005
Event message: Forms authentication failed for t

Answer 1

I've had the same issue after using a web.config from another machine. The problem was related with an invalid MachineKey. To solve the problem, I modified the web.config to use the correct MachineKey of my server.

This MSDN blog post shows how to generate a MachineKey.