Missing dependency problem on installing httpd-devel

I'm trying to install 'passenger-install-apache2-module' (for Rails) but it tells me I am missing:

• Apache 2 development headers... not found
• Apache Portable Runtime (APR) development headers... not found
• Apache Portable Runtime Utility (APU) development headers... not found

And then tells me how to install them:

• To install Apache 2 development headers: Please run yum install httpd-devel as root.

• To install Apache Portable Runtime (APR) development headers: Please run yum install apr-devel as root.

• To install Apache Portable Runtime Utility (APU) development headers: Please run yum install apr-util-devel as root.

But when I try:

yum install httpd-devel

I get:

Loaded plugins: fastestmirror, security Loading mirror speeds from cached hostfile Reducing Red Hat Enterprise 5 - x86_64 - Virtualmin Bleeding Edge to included packages only Finished Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package httpd-devel.i386 0:2.2.3-63.el5.centos.1 set to be updated --> Processing Dependency: httpd = 2.2.3-63.el5.centos.1 for package: httpd-devel ---> Package httpd-devel.x86_64 1:2.2.3-63.1.vm set to be updated --> Finished Dependency Resolution httpd-devel-2.2.3-63.el5.centos.1.i386 from update has depsolving problems --> Missing Dependency: httpd = 2.2.3-63.el5.centos.1 is needed by package httpd-devel-2.2.3-63.el5.centos.1.i386 (update)

Any ideas how I can fix this - I'm bound to be doing something obvious wrong :/