Some clients are experiencing the following error on Coldfusion 10 and 11.

Failed to set cookie. ColdFusion is unable to add the cookie you specified to the response. This is probably because you have used it to set one of the ColdFusion Session Cookies or Authentication cookie. Please use Application/Server level configuration for this.

To fix this, login to Coldfusion Admin, go to Memory Variables, and uncheck 'Disable updating Coldfusion internal cookies using Coldfusion tags/functions.' Save your settings and restart your website.