Animations won't render

I recently downloaded 2.45 (on a PPC mac, python 2.5) and now I cannot render my animations. Whenever I hit the animate button (and even the render button on occasion), I get a bunch of frames of the background. None of the objects in the scene appear. All layers are showing so I have no clue where they could be going to.

Any suggestions?

On the render layer tab there are TWO sets of layer buttons. Make sure that they match up. The buttons on the top row coincide with the layer buttons on the 3D window header and are simple visibility flags. The second row of buttons are the ones which actually define what gets rendered (from the layers defined as visible) on a per-render layer basis.

Okay, I feel like a total noob now. Did they change that default in 2.45? Because my multi-layered scenes have always rendered before.