yes now i'm 100% sure that there is something wrong in the fly-to-basket.js
i gotted rid of the block and added the:
<div id="shopping_cart">
<strong>Shopping cart</strong>
<table id="shopping_cart_items">
directly into the products.php page
and there also it act the same as in the block.
i really think something is missing in the .js
however unfortunaly i'm not the one to trace this bug down.