We have been developing a custom module for sometime now.  It has worked very well up until we upgraded our server from DNN 4.8.0 to DNN 4.8.2.  

Once we did that upgrade we started to get the following error message when we access certain portions of our project:

Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.

We made the adjustment to the web.config that was listed and that resolved the issue.   Sort of.   We found that the "inProc" session was fairly unstable and caused us a bunch of weird random session errors, where our session variables would be partially empty.

After a few days we decided to downgrade back to DNN 4.8.0 and change the Session back to "StateServer".  Immediately all errors went away.

I am looking for some insight into what changed between DNN 4.8.0 and DNN 4.8.2 that would cause the error? 

We can obviously change the way we serialize the object to get around the issue, but is that the best way to do it? 

Thank You,
Stuart

We are definitely trying to persists DNN Objects, such as UserInfo information.    I didn't see anything that jumped out to me either in the Change Log, that is why I have asked because I just haven't been able to track it down.

Thanks,
Stuart