Yum repo fails: "Cannot retrieve repository metadata (repomd.xml)"

I've got a personal yum repository that is suddenly broken. Nothing has been changed since the last time I tested it and everything was working. Here's what the repo file looks like:

[emergent]
name=emergent
baseurl=http://grey.colorado.edu/yum
gpgcheck=0

You can view the repo in a web browser: http://grey.colorado.edu/yum
Including the repomd.xml file: http://grey.colorado.edu/yum/repodata/repomd.xml

I created this repo with the `createrepo' command and no special options. If you have any troubleshooting advice I would greatly appreciate it. My test system is FC8.

Cheers,
Brian