Octave is not producing any plots in Mountain Lion. What is the problem?
This has something to do with the X11 and GNUPLOT, but it can be resolved with the following code in the Terminal:
cd /Applications/Gnuplot.app/Contents/Resources/lib
mv libfreetype.6.dylib libfreetype.6.dylib.bak
ln -s /usr/X11/lib/libfreetype.6.dylib .
It worked for me, hope it works for you as well.
Credits to Slava at http://octave.1599824.n4.nabble.com/Mac-OS-X-Mountain-Lion-Octave-can-not-execute-sombrero-td4643502.html