Can't get scripting to work

I tried to run “Center Glyphs” Script on the macro panel but it keeps giving me syntax errors.
Same thing when I install Robofab (I tried installing RoboFab inside Scripts folder as well as under Python/2.5/site-packages - none of them worked).

Here’s my latest output

Traceback (most recent call last):
File “Center”, line 31, in
File “Center”, line 19, in main
TypeError: ‘NSKVONotifying_GSFont’ object is not callable

Any thoughts on what should I do to fix it?

I’m on the app store Glyphs, Snow Leopard.

I updated the scripts in github. Can you please download them again?

Will do. Thanks