I can not make a checkout, the site freezes there and no error is raised
This Error Reference applies to:
Any version.
This Error Reference is intended for:
Any audience.
This is because SSL is now working on the checkout. To disable it, you can go to site setup -> get paid -> payment options -> uncheck SSL
If you need to have SSL working for your site, you can see some documentation on how to set it up here:
http://plone.org/products/getpaid/documentation/how-to/how-to-set-up-ssl-for-getpaid