[ESS] loading error

[Adrian Baddeley]

I am getting the following error while loading ESS (versions 5.1.0 and 5.2.3) 
in my .emacs file.
       Lisp error: (wrong-type-argument keymapp 1)

A debugger trace is appended below. The offending command is 
  copy-keymap(1)
appearing to arise from the line 
   (setq sas-mode-local-map (copy-keymap (current-local-map)))
in the file "essd-sas.el". 

I would appreciate any pointers on how to chase this down.

This is a basic home-area installation of ESS under Debian.
The error was not happening yesterday and I assume our Debian 
has been upgraded overnight.

thanks
Adrian Baddeley

;;;;;;;;;;;;; output of "emacs --debug-init"  ;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;; Byte codes replaced by "XXXX"   ;;;;;;;;;;;;;;;;;;;;

Debugger entered--Lisp error: (wrong-type-argument keymapp 1)
  copy-keymap(1)
  byte-code("XXXX" [current-load-list shell-mode-map comint-mode-map boundp nil make-sparse-keymap define-key "" shell-forward-command "" shell-backward-command "	" comint-dynamic-complete "¿" comint-dynamic-list-filename-completions [menu-bar completion] copy-keymap lookup-key [menu-bar completion] define-key-after [menu-bar completion] [complete-env-variable] ("Complete Env. Variable Name" . shell-dynamic-complete-environment-variable) complete-file [menu-bar completion] [expand-directory] ("Expand Directory Reference" . shell-replace-by-expanded-directory) complete-expand] 7)
  require(shell)
  eval-buffer(#<buffer  *load*<3>> nil "essd-sas" nil t)
  load-with-code-conversion("/u/adrian/emacs/ESS/ess-5.2.3/lisp/essd-sas.el" "essd-sas" nil t)
  require(essd-sas)
  eval-buffer(#<buffer  *load*<2>> nil "/u/adrian/emacs/ESS/ess-5.2.3/lisp/ess-site" nil t)
  load-with-code-conversion("/u/adrian/emacs/ESS/ess-5.2.3/lisp/ess-site.el" "/u/adrian/emacs/ESS/ess-5.2.3/lisp/ess-site" nil nil)
  load("/u/adrian/emacs/ESS/ess-5.2.3/lisp/ess-site")
  eval-buffer(#<buffer  *load*> nil "~/.emacs" nil t)
  load-with-code-conversion("/u/adrian/.emacs" "~/.emacs" t t)
  load("~/.emacs" t t)
  #[nil "XXXX" [init-file-user system-type user-init-file-1 user-init-file source alt ms-dos "~" "/_emacs" windows-nt directory-files nil "^\\.emacs\\(\\.elc?\\)?$" "~/.emacs" "~/_emacs" vax-vms "sys$login:.emacs" "/.emacs" t load file-name-extension "elc" file-name-sans-extension ".el" file-exists-p file-newer-than-file-p message "Warning: %s is newer than %s" sit-for 1 "default" inhibit-default-init inhibit-startup-message] 5]()
  command-line()
  normal-top-level()