Hi Eric,

here is an updated patch for handling this.

The idea is to allow ":" in mode's names and variables names.
No need to use two `looking-at' in this case I think.

I'll submit the patch to emacs-devel and apply it if it's good.

Thanks,

schulte.eric@gmail.com writes:

> === modified file 'lisp/files.el'
> --- lisp/files.el	2013-03-24 06:42:25 +0000
> +++ lisp/files.el	2013-03-28 23:09:26 +0000
> @@ -3058,7 +3058,11 @@
>  	       (while (and (or (not mode-only)
>  			       (not result))
>  			   (< (point) end))
> -		 (unless (looking-at "[ \t]*\\([^ \t\n:]+\\)[ \t]*:[ \t]*")
> +                 ;; The first of these next two regexs handles the
> +                 ;; case when a variable name includes a ":", such as
> +                 ;; the `org-babel-default-header-args:R' variable.
> +		 (unless (or (looking-at "[ \t]*\\([^ \t\n]?+\\)[ \t]*:[ \t]*")
> +                             (looking-at "[ \t]*\\([^ \t\n:]+\\)[ \t]*:[ \t]*"))
>  		   (message "Malformed mode-line")
>  		   (throw 'malformed-line nil))
>  		 (goto-char (match-end 0))