Cannot Output Server Side Session Values Back to Client Side

I’ve just found that I cannot read the value of server action $_SESSION variables (which have the [ ] output option ticked) back on the client side any more. I’ve tried a million ways and they just don’t appear.

Please tell me:

1. Am I going crazy (it feels like it today! )
2. Could something have become corrupted in my design
3. Are you finding this too?