"Use Menu Weight" box does not stay checked

On the Administer > Site configuration > Weight page, when I click the checkbox for "Use Menu Weight" and hit the "Save configurations" button, I get the "Settings updated" confirmation but the checkbox unchecks itself. I tried sorting some nodes in a view by weight to check if the setting itself had been made and the checkbox just didn't reflect it -- but the menu weights were not used.

I don't want to have to set weights for my nodes -- in every case, I would like to use the nodes' menu item weight. Has anyone else been able to get this feature to work?