I have a module at my DNN site, and created two users A and B who will see different interface of the module based on their "UserID-->Role". 

Here is my problem:

• User A logged into DNN and saw his interface correctly.
• Then user B logged into DNN and saw his interface correctly.
• However, at this point, user A sees user B's interface rather than the original/correct interface user A saw before User B logged in.

My question: how do I keep the session state of each user?  

Yes, it is a custom module.

So, are you storing the UserID in session, then using that info to determine what to display when a request is made to your module? For security purposes, it's always best to check that information every time a request is made to help prevent this very problem. If this is not the case, perhaps you could explain your situation in a little more detail and I might be able to help you better.

Thanks,

-Nathan