lenoir

The issue is solved. I can't exactly tell what solved it, but i created a new image field, checked the thumbnail view button, and it worked perfectly. Then i disabled the thumbnail view of the field that caused the problem, tested it, then enabled it again, and now the thumbnail preview seems to work.

I find the problem. I had this bit of code in the head that was causing the problem. I deleted it and now it's working. 
    switch ($language){         case "fr":             $user->language = $languages->get("fr");             break;         default:             $user->language = $languages->get("default");             break;     } I don't know why i had it there… 
Anyways, thanks for your help!!