While trying Markus Triska's linum.el, I've stumbled upon a redisplay
bug in the window margin.

I'm using

  GNU Emacs 23.0.50.1 (i386-mingw-nt5.1.2600) of 2007-09-19 on JUANMAB

compiled with

  gcc (GCC) 3.4.5 (mingw special)

A simple way to see the bug:

----- .emacs -----
(require 'linum)   ;; a recent version

(setq linum-format
      (lambda (line)
	(propertize (format "%d" line) 'face 'linum)))

(setq confirm-kill-emacs 'y-or-n-p)
------------------

And then:

 emacs
 M-x linum-mode <RET>   ;; while on the Welcome screen
 C-x C-c

Strictly speaking, it is not required to set `linum-format', but it is
easier to see the bug that way.

             Juanma