I am seeing artifacts from certain characters (e.g. "@") when I  
navigate through a buffer, or when Emacs moves the contents of my  
buffer.

For example, here's a buffer after loading:

    http://i28.tinypic.com/2079w7c.jpg

and here's what happens if I hit "ctrl-k" six times:

    http://i30.tinypic.com/2cdg6x0.jpg

The effects are more pronounced with white-on-black, which is my usual  
setup:

    http://i31.tinypic.com/30avqtj.jpg

Hitting control-L, running (redraw-frame (selected-frame)), or moving  
the cursor over the location makes the artifacts disappear.

This is OS X 10.5.7, Emacs 22.3.1 (downloaded from http://porkrind.org/emacs/Emacs-22.3-i386-10.5.7.dmg) 
, with no .emacs or other customizations. I've seen the same behavior  
with the latest CVS snapshot, and with the Carbon emacs package from http://homepage.mac.com/zenitani/emacs-e.htmlD 
. I've also seen similar behavior in Aquamacs.

Here's the ctrl-x ctrl-= output for one of the "@" characters;

   character: @ (64, #o100, #x40, U+0040)
     charset: ascii (ASCII (ISO646 IRV))
  code point: #x40
      syntax: . 	which means: punctuation
    category: a:ASCII graphic characters 32-126 (ISO646 IRV:1983[4/0])  
l:Latin
buffer code: #x40
   file code: #x40 (encoded by coding system undecided-unix)
     display: by this font (glyph code)
      -apple-monaco-medium-r-normal--14-140-72-72-m-140-iso10646-1  
(#x40)

Has anyone else seen this? I've been living with it for a long time,  
but it is slowly driving me crazy.

Thanks!
Jon