Shopping cart attribute items changing to £0.00

Ok... this may take some explaining.

I have set some products up with attributes. They are products that come in several sizes with a price for each one so i selected to add attribute price to base price and then made base price 0. This means that when a customer selects a product attribute it is really declaring what size they would like (e.g. 500gm). This is working fine and the customer can add this to cart. However if the customer goes to the shopping cart and changes the quantity of this product (i.e. from 1 to 3) then the product appears at £0.00 instead of multiplying the amount. It then lets the customer continue through checkout and purchase multiples of theses products for £0.00. This does not happen for our products that do not have attributes.

Any idea on how to fix this?

I am almost definate it is to do with the base price being set at £0.00. Any ways to get around this?

It should multiply the attribute price, seems odd that it doesn't. Do you have a preview link?

Yeah, it should do. And it does on the default template. I wasnt sure whether there was just something i needed to change in admin. Our developer is looking into it now. If nothing comes back then i will post link etc. Thanks for the reply.