I have a store in magento c.e 1.8 i have created categories but the category tree is not not showing up on product edit section.
I can see the categories in Manage Categories section.
Please help if someone know about this problem.
This Fix the issue (for me):
UPDATE catalog_category_entity SET children_count = (SELECT COUNT(*) FROM (SELECT * FROM catalog_category_entity) AS table2 WHERE path LIKE CONCAT(catalog_category_entity.path,"/%"));
Make a backup before execute the query.
I'm facing the very same problem checking the database we have the level category's attribute with a wrong value.
I solved running the query founds on this link
hope this helps other