local koji, yum FTP errors randomly on F11

[Michael Cronenworth]

When I send builds to my local koji, I sometimes get failures just 
because yum failed to download the initial build root. I'll get messages 
like this:

ftp://localhost/pub/fedora/updates/12/x86_64/unzip-5.52-12.fc12.x86_64.rpm: [Errno 4] IOError: [Errno ftp error] 500 OOPS: child died

It can be any random package, not just unzip. It seems my builds are failing more of the time than succeeding lately. Any ideas on what this means?

I've tried everything from turning off SELinux to changing settings with vsftpd. The koji server and external repo are both on the same, fully updated F11 install.

Thanks,
Michael