Cant get correct product to my cart when using discount on a attribute

[cecepee]

I have just found a new problem that i have not seen before, mainly because i never used this function before.

On some products i have color attributes, and on one of them i wanted to add some discount.
Scenario is; the product can be bought in black or in white. both have normally same price.
Now i wanted to get rid of some whites i had a few left of and the blacks where on zero left.
At normal state i let people purchase even if its not in stock due to the many and often delivery's of this product.
Anyway, if i want to choose white in the drop down list and press add to cart it wont give me the correct product.
It still gives me the black product for full price. i tested in many browsers, flushed cache and re tested with same result.
If i go back to the BO and the products info and change to deny orders when out of stock, then i finally can get the white product in my cart and to the discounted price.
But as soon as i have the back-order option set on allow it's not working again.
This also makes me wonder, what if i have 3 of each in stock and have same back-order option and the discount on the white attribute, will same thing happen, will i only be able to order the black product?
I have in the past gotten orders for both attributes but then i didn't have any discount.

Im still using 1.25 with a very simple theme.
Is this an error, or is it as M$ would have said "a feature" how its supposed to be?