Ahhh, check boxes... I can't say that I've done a lot of testing with them (yet)...

Is there a reason you have chosen to use check boxes instead of any of the other attribute types?

One reason I ask is because it is possible to add the product to the cart with no checkboxes marked (product is added with a cost of 0.00), it is also possible to add one product with 1 checkbox marked, but if two or more are marked from the same option name then sba has a problem (will work to resolve that regardless of your final decision in this matter.)

So, in testing the product referenced above, it is possible to add a product to the cart, but not two at the same time when using two or more check boxes.

If you would prefer to allow a customer to add x quantity of say Bramen & Mango and y quantity of Limoen & Koffie and press the add-to-cart button one time, then I would suggest adding product attributes grid to your installation instead of check boxes for this "arrangement".