Repeated package installation attempts with non-standard architecture (CentOS)

[dparrish]

150-packages
  Installing packages: httpd.x86_64 php.x86_64
  CMD: yum install -y httpd.x86_64 php.x86_64
  CMD: Loaded plugins: fastestmirror, protectbase, rhnplugin
  CMD: Loading mirror speeds from cached hostfile
  CMD: 597 packages excluded due to repository protections
  CMD: Setting up Install Process
  CMD: Package httpd-2.2.3-43.el5.centos.3.x86_64 already installed and latest version
  CMD: Package php-5.1.6-27.el5.x86_64 already installed and latest version
  CMD: Nothing to do