[Problem] No Wifi with RC3 on B+

[Thib]

Hi ! I'm French and new to Raspberry Bi+.
I want to build a media center and so i installed XBian on it. It was the RC1, my wifi usb key was working with it but i did not manage to connect my network (even if it was "seen"). I set up today RC3 in order to fix this. But now my key isn't working anymore.

Do you have any solution ?

Thanks a lot for your help !