I've noticed that when a user browses the webshop via Google translate, the 'add to cart' button stops working.
I'm using the gtranslate module from http://gtranslate.net/
gtranslate 3.0.x.32
joomla 2.5.11
VM 2.0.20b
When the user switches back to english (the sites default language) the 'add to cart' button works fine. Just not in any other language.