[ESS] emacs 24 "woe": file name completion does not work for me

[Martin Maechler]

I'm sure some emacs gurus (possibly among ESS core!) will be
able to help quickly,
and I assume it has affected others, that's why I post here.

I'm working with Emacs 23  or  Emacs 24, depending on the
computer (OS) I use. I have a habit to use
comint-dynamic-complete  very frequently (and have bound it to
C-M-Tab and similar keys as this relates to ESS behavior)
in TODO, README, etc files,  and also in *.R (or *.c) files when
referring to other source files.

Now, Help about it in Emacs 24 says 

 > comint-dynamic-complete is an alias for `completion-at-point'.

 > It is bound to <C-tab>, <C-M-tab>, <f24> TAB, <menu> TAB.

 > (comint-dynamic-complete)

 > This function is obsolete since 24.1;
 > use `completion-at-point' instead.

 > Perform completion on the text around point.
 > The completion method is determined by `completion-at-point-functions'.

and if I look at the 
    completion-at-point-functions

it says
 
 > completion-at-point-functions's value is
 > (tags-completion-at-point-function)

and "of course" that has nothing to do with file name
completion, and so I should not wonder why file name completion
has stopped working for me, since I (am / had to start) using
emacs 24.

Now this makes using Emacs 24 really  a much less pleasant
experience for me.

Comments / Hints / Different experiences ?

Thanks in advance:
Martin