Hi Sergio,
There are some strange thing going on with the JSON and AJAX calls on your website. Those events need to be investigated, it might cost me hours and hours to resolve the problem. So instead, I should better refund you.
I don't know who is guilty about this issue though and i don't know if the problems will be ended once you disable our module, but you should better unpublished/uninstall our drop down shopping cart from your store (don't forget the vm2_cart plugin). Try to find an alternative shopping cart module that works fine with your current virtuemart structure.
You should be receiving an email from paypal momentarily that include detailed information about the refund transaction.
UPDATE: i looked at our backend and saw that you purchased the extension on 07 June 2013, which is more than 90 days ago. PayPal doesn't let us refund any payment if it has been placed more than 90 days ago. So i can't refund you, but i can replace your product with one of our $18 modules, free of charge:
Fancy Product Slider:
www.flexiblewebdesign.com/Virtuemart-Modules/Virtuemart-Flexible-Fancy-Product-Slider
or Product Scroller:
www.flexiblewebdesign.com/Virtuemart-Modules/Virtuemart-Flexible-Product-Slider
Please let me know which one you would like to me replace your drop down shopping cart module with.
Regards,
Support & Development