[CentOS] problem with yum on centos4.7

Hi all,

Sorry for this newbie question. I am having a problem with yum on centos 4.7. When I try something like "yum update" I get the following error:

file:///misc/CO4/updates/repodata/repomd.xml: [Errno 5] OSError: [Errno 2] No such file or directory: '/misc/CO4/updates/repodata/repomd.xml' Trying other mirror. Cannot open/read repomd.xml file for repository: update failure: repodata/repomd.xml from update: [Errno 256] No more mirrors to try. Error: failure: repodata/repomd.xml from update: [Errno 256] No more mirrors to try.

I've tried "yum clean all" with no success. I'd be grateful for any help that I could get on this. Thanks.

-tim