Go to phpMyAdmin ...
Find your database ...
Browse the products table ...
Sort on the fields:
products_quantity_order_min
products_quantity_order_units
Do you find a bunch set to 0 ...
These cannot be 0 they should be at least 1
If all are set to 1 ... make sure your Admin and Catalog configure.php files are both using the same database information ...
Otherwise, fix these with:
PHP Code:
UPDATE products SET products_quantity_order_min=1;
PHP Code:
UPDATE products SET products_quantity_order_units=1;