update时出现问题了

woody123

显示这些错误：Loading "installonlyn" plugin
Setting up Update Process
Setting up repositories
core                                                                 [1/3]
http://dxmirror.vmmatrix.net/Fed ... epodata/repomd.xml: [Errno 4] IOError: <urlopen error (22, '\xe6\x97\xa0\xe6\x95\x88\xe7\x9a\x84\xe5\x8f\x82\xe6\x95\xb0')>

Cannot open/read repomd.xml file for repository: core
failure: repodata/repomd.xml from core: [Errno 256] No more mirrors to try.
Error: failure: repodata/repomd.xml from core: [Errno 256]
换了几个站点都不行，求救，谢谢了！
我的repos文件是这么写的：
[core]
name=Fedora Core $releasever - $basearch
#baseurl=http://download.fedora.redhat.com/pub/fedora/linux/core/$releasever/$basearch/os/
baseurl=ftp://ftp3.tsinghua.edu.cn/mirror/download.fedora.redhat.com/pub/fedora/linux/core/5/i386/os
mirrorlist=http://fedora.redhat.com/download/mirrors/fedora-core-$releasever
enabled=1
如果不加了TSINGHUA的镜像点，升级时说找不到合法的镜像点，什么原因啊，配置有误 吗？