Hi,
The problem comes from the cufon replacer that you're using on your website (
extensions.joomla.org/extensions/style-a...ign/typography/11243
).
extensions.joomla.org/extensions/style-a...ign/typography/11243
In HikaShop, when you use characteristics, all the information of all the variants is stored on the page but only the current variant's information is displayed. The product name is also included in a h2 tag.
The cufon replacer replace the content of the h2 tag so the product name of the default variant is displayed with the cufon settings. But all the other viarants data is not replaced by cufon because they aren't in a h2 tag (they don't need to actually).
To solve the problem, you can either deactivate cufon, or edit the file show of the view product via the menu Display->Views and change the code:
<div id="hikashop_product_name_<?php echo $variant_name;?>" style="display:none;">
<?php echo $variant->product_name;?>
</div>
by:
<h2>
<div id="hikashop_product_name_<?php echo $variant_name;?>" style="display:none;">
<?php echo $variant->product_name;?>
</div>
</h2>
It's not sure that it will work but it should.