Content of the textarea outside of the editor

Hi everyone, i'm asking for your help 'cause i've got a weird issue, i'm loading CKEditor in a popin (in a lightbox) and when i'm loading it the content of my textarea is rewritten in a span and this span is outside of the textarea (and so the content of the textarea is now empty).
So i don't understand how it can happen! That's why i'm asking help.

Here is a screenshot of the loaded content:


I use colorbox for my lightbox and jQuery Form Plugin for the forms handling.

Does anybody have an idea?

Thanks for your help!