CustomItemGenerator and the Page Editor

CustomItemGenerator and the Page Editor

Sitecore 6.6 Update 4
We're using CustomItemGenerator 1.0 and I was using this to help build a
primary navigation menu for a site. This worked as expected and everything
was rendered properly.
My problem is when I attempt to edit the menu via Page Editor; I don't
even see the menu.
I use a repeater and repeat over a list of links to include in the nav.
Due to the way the HTML was created, each LI element needs to have its
own, specific ID ("Nav Id" Field in Sitecore) that ties into the CSS. Code
inside of my repeater's ItemDataBound event:
// Cast the item using CustomItemGenerator-generated class
GenericContentPageItem navItem = (GenericContentPageItem)e.Item.DataItem;
liMenuItem.ID = navItem.NavId.Rendered; // I tried "navItem.NavId" by
itself as well
So while this renders properly in the browser, it doesn't when I'm in Page
Editor:
<li id="<input
id='fld_B72EB6696DCF41A49671972D5EA5DEB8_2163B90C08AB4A18970A7F3ECE79DCFC_en_1_f71bd37d18d146c19e222e89fcffe278_3'
class='scFieldValue'
name='fld_B72EB6696DCF41A49671972D5EA5DEB8_2163B90C08AB4A18970A7F3ECE79DCFC_en_1_f71bd37d18d146c19e222e89fcffe278_3'
type='hidden' value=" Home?="">
... instead of it rendering like this:
<li id="Home">...</li>
Now, that having been said, I can change my code to not use the
CustomItemGenerator and it works fine in the browser and Page Editor as
follows:
GenericContentPageItem navItem = (GenericContentPageItem)e.Item.DataItem;
Item nav = Sitecore.Context.Database.GetItem(navItem.ID);
liMenuItem.ID = nav.Fields["Nav Id"].ToString();
I would like to avoid having to hardcode field names in my code, which is
why I am using CustomItemGenerator. Is there something that I'm doing
wrong with my code that it doesn't want to work in Page Editor?
Thanks!