FormsAuthentication.SetAuthCookie results in System.Security.Cryptography.CryptographicException: Bad Data when decrypting

Hello,

I am having problems with the SetAuthCookie.

FormsAuthentication.SetAuthCookie(userName, false);

When I am using it on my machine, I am getting the CryptographicException when I am decrypting it.

FormsAuthenticationTicket authTicket = FormsAuthentication.Decrypt(cookieValue);

If I am using the value of the cookie generated on another machine (at debugging time I can insert this value), the Exception does not occur. ALso strange, the cookie value generated by my machine is longer than the one generated by the other machine. My machine fails and the other one succeeds.

Any suggestions? Is there some overall machine or web.config setting I need to change?
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