Cataloger module - new attributes won't display for existing products

[mthacker]

I'm still setting up and customizing the Cataloger pages, and am running into a frustrating problem.  If I add a new custom Item Attribute, any product page created before then will not save text entered into the new attribute field.  Am I doing something wrong, or is it not possible to change the attributes for existing products? Or is there a better way to do this?  I worry because my client is very likely to want to adding/editing/remove the attributes, and I was hoping it would updated all products automatically. Please help!