Dear PyMOL Users

For some reason transparency on surfaces are not working. I have tried setting the transparency using the command line (set transparency, 0.5) and using the menu bar both before and after I apply the surface to my molecule, but no combination works!

I am using MacPyMOL, (v1.3), on a Mountain Lion OSX MacBook Pro.

Am I doing something wrong, or is there something more amiss here?

Many thanks for any help,
Gareth Price