Since we updated WP to the last version (3.7.1) we have been having the same problem trying to proceed from checkout page.
When you click proceed to confirmation it simplly reloads checkout page. Doesn't display a warning even if you leave all the fields black, and does the same with every purchase gate.
We have tested with all the plugins disabled, with a different theme, with a fresh eshop installation, changing the general config, and still the same.
Please help with some solution if someone has have the same issue. Site is hidroshop.mx
Thank you so much!