Hoje estava com um problema quando executava o Ghostscript
~/Sites/rails > gs
dyld: Library not loaded: /opt/local/lib/libpng12.0.dylib
Referenced from: /opt/local/lib/libcairo.2.dylib
Reason: Incompatible library version: libcairo.2.dylib requires version 34.0.0 or later, but libpng12.0.dylib provides version 33.0.0
Trace/BPT trap
Solução? desativar e ativar novamente a lib
sudo port deactivate libpng
---> Deactivating libpng
sudo port activate libpng
---> Activating libpng
Pronto
~/Sites/rails > gs
GPL Ghostscript 8.63 (2008-08-01)
Copyright (C) 2008 Artifex Software, Inc. All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
GS>