debian unstable update and emacs looses R

[Angel Lopez]

I've updated my debian linux unstable this week. After the update 
everything is fine except for emacs not being able to open an R session, 
when I type M-x R , I get a [No match] reply in the minibuffer. R 
installation is fine (i.e. typing R in bash starts R normally) and I've 
also tried running emacs as root but the problem is still there.
Emacs version is 21.3.1
BTW with other programs (e.g. M-x maxima) works fine so it seems to be 
an R only problem.

Any hints on where might be the solution.
Thanks,
Angel