Unknown Login Error Code 0x5

Behavior:

1. Login to DocuWare Windows Client
   "Unknown Login Error Code 0x5. Please check your login and verify that all DocuWare components are working correctly."
2. Login to DocuWare Administration:
   "An error occurred please contact the administrator with the following information:  Object reference not set to an instance of an object."

Reason:
FIX version of the DocuWare Client differs from the FIX version of the Authentication Server.

Solution:
Install the same FIX on the DocuWare Servers and all DocuWare clients.

Trouble Shooting possibilities:

1. Telnet Authentication Server
2. Netstat Authentication Server port
3.  occurs the problem on every client or only one client?
4. were the server services updated and the client not?
5. Is a firewall installed?
6. Is the Authentication Server port opened in the firewall?
7.  extended Logging with adapted DocuWare.Wrapper.DW4Client.dll.config