[pygame] libpng problem on OS X (intel)

[Nathan <nathan.stocks@xxxxxxxxx>]

I haven't actively done anything with my pygame project
"nathancheckers" since my daughter was born over a year ago.  I've got
a MacBook Pro (core 2 duo, 2GB RAM) and I use MacPorts to install
pygame and stuff like that.  I checked when I fiirst got it, and
nathancheckers seemed to run fine at the time.  Now it fails with the
following error, which I can't figure out.

$ ./nathancheckers.py
Traceback (most recent call last):
  File "./nathancheckers.py", line 26, in ?
    from nc_display import *
  File "/Users/nathan/nathancheckers/tags/1.5/nc_display.py", line 82, in ?
    set_theme()
  File "/Users/nathan/nathancheckers/tags/1.5/nc_display.py", line 33,
in set_theme
    global g_board;        g_board        = l(j('themes',theme,'g_board.png'))
pygame.error: Failed loading libpng12.dylib: dlopen(libpng12.dylib,
2): image not found

I've manually checked that the image it wants still exists in the same
location it always had.  I've upgraded MacPorts and everything in it
(including libpng and pygame) to the latest versions.  The .dylib file
exists:

$ locate libpng12.dylib
/opt/local/lib/libpng12.dylib

Any ideas?  nathancheckers is open source.  You can download the full
source and everything here (the "linux" download is the full source
tarball):

http://www.stocksfam.com/nathancheckers/

Any ideas???