Yum error - parser error : Space required after the Public Identifier

[logart]

I am getting a weird error all of the sudden when running any yum command:

yum update
Setting up Update Process
Setting up Repos
contrib 100% |=========================| 328 B 00:00
//var/cache/yum/contrib/repomd.xml:1: parser error : Space required after the Public Identifier

^
//var/cache/yum/contrib/repomd.xml:1: parser error : SystemLiteral " or ' expected

^
//var/cache/yum/contrib/repomd.xml:1: parser error : SYSTEM or PUBLIC, the URI is missing

^
Cannot open/read repomd.xml file for repository: contrib
Error importing repomd.xml from contrib: Error: could not parse file //var/cache/yum/contrib/repomd.xml


Any ideas?

[logart]

debugging yum has shown me that the URL is wrong:

http://beta.centos.org/centos/4.0beta/contrib/i386/ does not exist. The i386 folder is missing all of the sudden.