I have been translating my site into Japanese using WPML. If I try to create an account at /ja/register/, I get stuck in a loop at the username/email/password phase of registration. I enter my info and the page just reloads. I cannot go to the next step where you get the option to apply a coupon.
However, if I create an account with the English page, and then go back to ja/register then I can use my code and continue as usual.