Thanks for the quick response, Massimo. I checked the cookie id and it's getting blasted away. Somehow, the session_id_myapp is changing. Don't know why as I don't know what I've done to change it. I am setting other session variables, but never touched the session_id_myapp variable.
I'm running under Windoze NT and web2py 1.79.2. As I said, this has been working but just stopped cold last night. I imagine I broke something, but don't really know where to start looking.