[Plugin: Cimy User Extra Fields] Hidden fields translate problem

Hi,
Thanks for such a great plugin, I’m using it and everything is ok except something that i searched hours and hours to resolve it, even made change in wordpress language files, but finaly, nothing.
So I ask it here and hope you can help me.
When I’m using wordpress hidden fields in registration form they will shown in English, I’m using WP 3.3.2 official Persian language translation. I made a simple .po file for plugin (as mentioned in plugins homepage) and translated few words and sentences that shown to front-end user and thats works but not for hidden fields like : First name, Last name and Password Confirmation. They are still in English !
This is really confusing me.
Thanks.

https://www.ads-software.com/extend/plugins/cimy-user-extra-fields/