DOF in Blender 2.5?

I’m trying to figure out how to do just a simple DOF setup in Blender 2.5.
This is what I’ve got so far
It was created in blender 2.5 SVN ~22096 (I can’t tell but I built it today) Ubuntu 9.04 x64
I cannot get it to focus properly on the second box in the view of the blend file.
I’ve dropped the fstop value to ~2 (Trying various points between 128 and 2) which should make it fairly obvious on what it is focused on.

What am I doing wrong?

Thanks for any input.

i’d say you tied the focus of the camera to the empty and forgot about it. (currently residing at the third box)
either remove the emtpy from the input below “Depth of Field:” in the cameras settings panel and tune the distance again or move the empty around to the second box.
both ways worked for me.

Thanks next time I’ll remember place the empty where I expect the empty.

Again thanks for the help. What is with the flickering when I render this now?
Here is the current blend file

Never mind, it seems like the Approximate Ambient Occlusion settings I was using seem to have an issue that causes the flickering.

Approximate will flicker. You can turn up the correction, this may help. Or turn down the error (increases time).

Thanks Atom for the gentle nudge in the right direction.