But after importing language file

Hi !
I've recently imported my .po language file to make some translations.
From that moment on all the headers / titles (i think the ajax controls) are a simple text.
So I can't open it. E.g.:
Publishing options in a create content page are now simple text, but that was a clickable header earlier
I don't know what happened, it's like the javascript or what disappeared..

Any idea?

Thank you