in product edit page, existing product categories can be unchecked, but the rest of the categories cannot be checked -- which means i cannot add product to categories from product edit page.
once i uncheck a category, and save, it is grayed out and cannot be checked again.
there is an exception, i can add new products to any category, but once the product is listed i cannot add it to new categories from product edit page.
i can though add products to a category from category edit page.
magento 1.9.0.1
anyone who can help? thanks!
