All of my names are ok. I have checked and double checked, and then went back and checked again.

But I think I figured it out. I somehow lost my
define('TEXT_INFORMATION', ''); from my custom file.

So I guess it was taking the
define('TEXT_INFORMATION', 'You may want to add some instructions for using the shopping cart here. (defined in includes/languages/english/shopping_cart.php)');
from the default file.

So putting the define statement in my custom file seems to have fixed things.

Does that sound right? It would take a single define from the default file, but still use the custom file for any new defines that are listed there?