Unable to use yum repos whether with baseurl or mirrorlist in CentOS 6.5

Since a couple of days, I'm unable to retrieve repositories data with Yum, in my CentOS 6.5 server. I did yum clean all a dozen of times, it emptied all but didn't solved the problem. I tried to retrieve things by restricting to the single base repo : [base] name=CentOS-$releasever - Base mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6 yum --verbose update results in : Loading "fastestmirror" plugin Loading "priorities" plugin Config time: 0.010 Yum Version: 3.2.29 Setting up Package Sacks Determining fastest mirrors Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os error was 14: PYCURL ERROR 22 - "The requested URL returned error: 403 Forbidden" Error: Cannot find a valid baseurl for repo: base And when I configure a baseurl instead of a mirrorlist, I get this : Loading "fastestmirror" plugin Loading "priorities" plugin Config time: 0.010 Yum Version: 3.2.29 Setting up Package Sacks Determining fastest mirrors http://mirror.centos.org/centos/6/os/x86_64/repodata/repomd.xml : [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found" Trying other mirror. Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again The server pings mirror.centos.org and I can reach without any problem the mirrorlist and the repomd.xml in a web browser. Disabling the plugins changed nothing. The mirrorlist gives a 403 error and a baseurl 404... rpm -q --verify -f /etc/yum.repos.d/* results in : S.5....T. c /etc/issue .......T. c /etc/yum.repos.d/CentOS-Base.repo .......T. c /etc/yum.repos.d/CentOS-Debuginfo.repo .......T. c /etc/yum.repos.d/CentOS-Media.repo .......T. c /etc/yum.repos.d/CentOS-Vault.repo S.5....T. c /etc/issue .......T. c /etc/yum.repos.d/CentOS-Base.repo .......T. c /etc/yum.repos.d/CentOS-Debuginfo.repo .......T. c /etc/yum.repos.d/CentOS-Media.repo .......T. c /etc/yum.repos.d/CentOS-Vault.repo S.5....T. c /etc/issue .......T. c /etc/yum.repos.d/CentOS-Base.repo .......T. c /etc/yum.repos.d/CentOS-Debuginfo.repo .......T. c /etc/yum.repos.d/CentOS-Media.repo .......T. c /etc/yum.repos.d/CentOS-Vault.repo S.5....T. c /etc/issue .......T. c /etc/yum.repos.d/CentOS-Base.repo .......T. c /etc/yum.repos.d/CentOS-Debuginfo.repo .......T. c /etc/yum.repos.d/CentOS-Media.repo .......T. c /etc/yum.repos.d/CentOS-Vault.repo .......T. c /etc/yum.repos.d/epel-testing.repo .......T. c /etc/yum.repos.d/epel.repo .......T. c /etc/yum.repos.d/epel-testing.repo .......T. c /etc/yum.repos.d/epel.repo le fichier /etc/yum.repos.d/isv:ownCloud:community.repo n'appartient à aucun paquetage .......T. c /etc/yum.repos.d/jpackage.repo le fichier /etc/yum.repos.d/jpackage.repo.rpmsave n'appartient à aucun paquetage « n'appartient à aucun paquetage » means « doesn't belong to any package », in french... Those problems occur with whatever repo I enable/disable.