Hello again, I've opened my .emacs file and "refreshed" it by clicking on the menu Emacs-Lisp > Evaluate Buffer. After doing this, somehow EMACS now knows it must put code within MINTED environment in the .tex file and not use LISTINGS instead.
I guess Nick was right -- my EMACS doesn't see its init file every time I launch it by double clicking the icon!
Now that's matter for another thread...