[Problem] No Wifi with RC3 on B+

[Thib]

I have an error when I want to install git :

Terminal

Failed to fetch http://mirrordirector.raspbian.org/raspbian/pool/main/g/git/git-man_1.7.10.4-1+wheezy1+rpi2_all.deb Hash Sum mismatch
Failed to fetch http://mirrordirector.raspbian.org/raspbian/pool/main/g/git/git_1.7.10.4-1+wheezy1+rpi2_armhf.deb Hash Sum mismatch
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

And without git, I can't clone the repository

PS : apt-get update makes an error too :
W: Failed to fetch xz:/var/lib/apt/lists/partial/mirrordirector.raspbian.org_raspbian_dists_wheezy_main_binary-armhf_Packages Hash Sum mismatch

E: Some index files failed to download. They have been ignored, or old ones used instead.