No subject

would put libpng.so.2 into /usr/lib/, which should definitely
be found.  If libpng.so is anywhere else, say /usr/local/lib,
it may be that the system doesn't know to look there for shared
libs.  This is a pretty common problem on linuxes, but can be
fixed by editing the ld.so.conf file (usually /etc/ld.so.conf),
which is just a plain text file of the directories to look for
shared libs.  A typical one might include:
   /usr/lib/
   /usr/X11R6/lib/
   /usr/lib/qt-2.3.0/lib/
   /usr/lib/mysql/
   /usr/local/lib

You might have to add '/usr/local/lib' or wherever libpng.so
is, and then run 'ldconfig'.

Hope that helps,

--Matt