Thanks for your anwer. I’ve checked all you’ve told me.
I’ve solved the checkout issue.
But the issue adding to a cart a variable product in second language is still not working. I’ve tried with twentytwelve template and I’ve resaved all atributes,and I’ve the same issues.
It doesn’t gone away after “Save Changes”. I’ve hide the debug info in wp-config.php and now is not visible. Now this is not really a problem for me, but there was something wrong in your code.
I don’t have this protection. And I try by changing the permission to read, write and execute of this folder and it continue the same. Doesn’t work if I was not logged.