Hi,
I’m using Blender 2.57b in a Macbook Pro and it was working fine, but when I opened it today, I wasn’t able to scale meshes in object mode by pressing s-key and dragging the mouse. It works in edit mode, but not in object mode.
Regards
Turn off the “Manipulate object centers only” button in the 3d view header (three dots above a double-headed arrow).