You are most certainly experience a "incompatibility" between the add-on that you use for multiple languages and the Easy Fancy-box (wordpress Plugin).
As Wordpress does not support multiple languages natively, most of the plugins available do not support it either. For more information about multiple languages, please see What are options are there to implement a multi language site.
To find a solution for your issue, you need to find out how a plugin can support your multi-languages feature. You have not written how you added multiple languages to your blog, so this can not be answered with your question. If done by a plugin you normally find the information for that on the plugins homepage or forum or in the wordpress support forums provided by other users.
Now that you added that you're using the qtranslate (Wordpress Plugin), you can do the following: Ensure that this is not a configuration issue on your side. If not, get in contact with the author of the fancybox plugin and tell that you would love to see it offering compability with a multi-lingual site with qtranslate. qtranslate is quite popular so some plugin authors are willing to add support for it.