The AD FS Web Agent for Windows NT token-based applications encountered a serious error. The client was successfully authenticated ...

The AD FS Web Agent for Windows NT token-based applications encountered a serious error. The client was successfully authenticated using the token from the Federation Service, but the Web agent was not able to redirect the client back to the application page that was originally requested. 

User Action 
If this error persists, enable the AD FS troubleshooting log.