Button not appearing on nav group on iPod Touch?

I have an app that uses a navigation group. On the last step, I have a system button that calls a "start over", which closes all the views and returns to the beginning (and resets some saved data):

http://pastie.org/1835626

The initial view has a toolbar button, which I labeled "begin":

It works fine on my iPhone 4 and on a 3GS, but on a 1G iPod touch, there is no Begin button when the start over is run. I need to quit and relaunch. All 3 devices are on 4.3.2.