R typically installs libgfortran so packages can link to it, but for some reason it wasn't linked properly for me.
ln -s $(R RHOME)/lib/libgfortran.2.dylib $(R RHOME)/lib/libgfortran.dylib
Also for some reason R wasn't able to find its own shared library directory, so download geiger
curl -O https://dl.dropbox.com/u/8859543/geiger_1.4-4.666.tar.gz