Ok, thanks. I've solved my problem. I'm not sure that's the way I was supposed to do it but I simply removed the original global.asax to replace it by my own and it started using my provider... go figure... Before I came to this solution, I even tried renaming a bunch of things in global.asax (even the namespace) and I couldn't break anything... It was almost like  the chat system was not even using the file but I knew it wasn't the case because renaming the global.asax file had an effect.

 

Anyway, I'm slowly getting where I want to be. Thanks.