Missing profile fields in the registration form and other wonky behaviour

I have a multi-language site that I recently moved from a development folder to a public folder and all seemed well, at first.

The user registration forms that were previously working just fine no longer display any of the custom profile fields; they will only display the account fields (email and username).

What's even odder is that this behaviour only occurs when the URL includes a language prefix. For example...

http://www.encuentramascota.com/es/user/register
http://www.encuentramascota.com/en/user/register

... fail to show the profile fields. However,...

http://www.encuentramascota.com/user/register

... shows the registration form with the profile fields just fine. Since the default language is in English and I need the Spanish version for most of the users, this is a major problem for me.

I've spent hours trying to figure it out. I have a custom form template called user_register.tpl.php that constructs the form using form construction items as in ...

print drupal_render($form['Contact']['profile_address_1']) ;

When I output the $form variable at the user_register.tpl.php file, it shows no sign of the profiles sections (Contact, Information 1, etc.)

I've checked the modules against a similar site I have working properly on a different server and everything checks out. All the profile fields are set to display in the registration form and all the permissions are correct.

Any ideas?

Cheers
Roland Combes