One thing to note about Astaran's session suggestion is that you are passing the authentication on your servers. At the moment every time the board needs to retrieve the user number or the languate it queries the cookie which is local to the client. In the session suggestion this will be on the server which will increase the queries on your database, your bandwidth and the load on your server.
If you want to do this with cookies you will need to modify the code quite a bit to use the same cookie. What I was thinking is when the user goes to server 1 the cookie gets created and the user is logged in. When the user wants to access the data on the server 2 then it reads the cookie that the server 1 produces so that it authenticates the user. The name of the cookie 1 can be stored in a variable on the boards. If the authentication information is not found in the cookie produced by server 1 then it will be searched on the cookie of server 2 and vica versa.
