Since no one has suggested any fixes for this issue introduced in the forum a year ago, I have to believe this is a bug. We first ran into is in 1.5.6 - right after I upgraded the website.

I have now set up a demo site with 1.5.7 I copied over the products, attributes etc table from an upgraded 1.5.7 database. I made sure the structure of those tables match the default database.

There are over 57,000 entries in the attributes table. When trying to add new attributes in admin (remember this is default 1.5.7d), no option values appear when one clicks on an option name.

I have noted 2 messages in Chrome's developer tools but turns out one happens as soon as you enter the attribute controller for a product.

the first error before selecting an option value:
index.php:1 Uncaught RangeError: Maximum call stack size exceeded

the second error once a option value is selected:
attributes_controller.php?products_filter=9401&current_category_id=610:834 Uncaught ReferenceError: update_option is not defined
at HTMLSelectElement.onchange (attributes_controller.php?products_filter=9401&current_category_id=610:834:221)

The client is presently totally unable to add products due to this problem.