swfu is undefined when i upload media

Hello....

I have a bug when i want upload a media...
A choose an image, and press upload. when the upload is done, i have white screen and i can't edit info of media.

In firebug i have :
swfu is indefined
switchUploader(1) load-scr...9e2f304d2 (ligne 166)
swfuploadPreLoad() load-scr...9e2f304d2 (ligne 166)
anonymous() load-scr...9e2f304d2 (ligne 158)
anonymous() load-scr...9e2f304d2 (ligne 158)

I don't understand..

Thank you all :x