Yum sur CentOS-5.3

Bonjour,
j'ai un souci avec Yum quand je tape Yum install rlog par exemple j'ai ce message:

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. $releasever is not a valid release or hasnt been released yet/
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. $releasever is not a valid release or hasnt been released yet/
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. $releasever is not a valid release or hasnt been released yet/
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. $releasever is not a valid release or hasnt been released yet/
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. $releasever is not a valid release or hasnt been released yet/
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. $releasever is not a valid release or hasnt been released yet/
* c5-media:
http://mirror.centos.org/centos/%24releasever/os/i386/repodata/repomd.xml: [Errno 12] Timeout: <urlopen error timed out>
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again
[root@localhost ~]#

Merci de m'aider à gérer ce problème pour que je puisse faire les mises jours sur mon serveur.