Frank,

>Bernard,
>
> >  >The new definition of add@accent is supposed to keep correct
> >  >spacefactor's after accented uppercase letters. The cost is
> >  >that a command like \edef\agrave{\`a} will not work as
> >  >expected (with respect to spacefactors).
> >  >More importantly, this makes the babel package fail,
> >  >and possibly others.
[...]
>within standard LaTeX the new defnition of \` and friends still work
>perfectly
>in all circumstances. the fact that inside babel \edef was used in a place
>where \protected@edef should have been used was an oversight and is
>corrected.

The "expandability" of \add@accent has not changed. It is still
expandable, if its definition is:

\def\add@accent#1#2{{%
   \setbox\@tempboxa\hbox{#2%
      \global\mathchardef\accent@spacefactor\spacefactor}%
   \accent#1 #2}\spacefactor\accent@spacefactor}

The problem is that \accent@spacefactor is not yet defined in \edef's
prior to an actual use of any accent. That is a LaTeX bug which can be
fixed by letting \accent@spacefactor to \relax or by defining
it with \mathchardef (in both cases it expands into itself).

Example:

\documentclass{minimal}

\edef\agrave{\`a}  % Doesn't work
\setbox0\hbox{\`a} % We use an accent
\edef\agrave{\`a}  % Now it does work (but \agrave looks horrible! :-) )

Regards
Javier Bezos