[ESS] File mode specification error: (void-function run-mode-hook)”.

[Richard M. Heiberger]

I suspect you have something in one of your initialization
files that conflicts with ESS.
Please close emacs and reopen emacs without your own
initialization files.

emacs -q --no-site-file


Then start ESS from the *scratch* buffer with

(load "~/ess/ess-5.3.10/lisp/ess-site") C-j

If this works, then you will have to investigate
where in site-start.el or .emacs the conflict exists.

Please report back to the list with success or further
information.