Object scale hotkey (S) not scaling objects?

I just started up Blender today, opened a project I’ve been working on, and tried to add a new object for which I needed to scale. I pressed ‘S’, the line came up and the cursor changed, but it did not change the object. Resizing via the object properties tab works fine, but it’s extremely inconvenient.

Edit: Using the transformation manipulators button at the bottom of the default view doesn’t work either. I can rotate or move objects. I’m working in Blender 2.68.

Edit again: It works fine in edit mode.

Is the Manipulate Center Points button activated? If so, deactivate it.

If that doesn’t help, post your .blend file so we can see what the problem is.