[CentOS] Yum update fails

I updated my centos 4.5 server to centos last week and I am now getting
errors when I attempt to do a yum update:

[root at AJD-slag ~]# yum update
Loading "installonlyn" plugin
Plugin "fastestmirror" uses deprecated constant TYPE_INTERFACE.
Please use TYPE_INTERACTIVE instead.
Loading "fastestmirror" plugin
Setting up Update Process
Setting up repositories
update                    100% |=========================|  951 B
00:00
base                      100% |=========================| 1.1 kB
00:00
addons                    100% |=========================|  951 B
00:00
extras                    100% |=========================| 1.1 kB
00:00
Determining fastest mirrors
Traceback (most recent call last):
  File "/usr/bin/yum", line 29, in ?
    yummain.main(sys.argv[1:])
  File "/usr/share/yum-cli/yummain.py", line 94, in main
    result, resultmsgs = base.doCommands()
  File "/usr/share/yum-cli/cli.py", line 381, in doCommands
    return self.yum_cli_commands[self.basecmd].doCommand(self,
self.basecmd, self.extcmds)
  File "/usr/share/yum-cli/yumcommands.py", line 150, in doCommand
    return base.updatePkgs(extcmds)
  File "/usr/share/yum-cli/cli.py", line 672, in updatePkgs
    self.doRepoSetup()
  File "/usr/share/yum-cli/cli.py", line 104, in doRepoSetup
    yum.YumBase.doRepoSetup(self, thisrepo=thisrepo)
  File "/usr/lib/python2.4/site-packages/yum/__init__.py", line 313, in
doRepoSetup
    self.plugins.run('postreposetup')
  File "/usr/lib/python2.4/site-packages/yum/plugins.py", line 153, in
run
    func(conduitcls(self, self.base, conf, **kwargs))
  File "/usr/lib/yum-plugins/fastestmirror.py", line 78, in
postreposetup_hook
    repo.set('urls', repomirrors[str(repo)])
AttributeError: 'YumRepository' object has no attribute 'set'

Any suggestions, Google has not been my friend today.

Thanks, 

Aron