On Emacs, I used to have "C-c C-e" as a shortcut to "open an environment with begin and end". I changed my computer and reinstalled emacs: Mac OS 10.9 and Emacs 24.3, and now in LaTeX mode, "C-c C-e" is only closing an already opened environment. (it seems that "C-c C-t" is doing roughly the same as before but not exactly)
Similarly, "C-c C-s" is not opening a new section anymore.
Finally, "C-c C-;" used to comment region, but is not working anymore.
Any idea on how I could come back to the previous behaviour? (I don't know the name of the commands and I fail to rebind C-c C-e...)