Hi Andy,
Are you using Mellanox OFED, or the CentOS 6.4 supplied Infiniband drivers?
If you're using Mellanox OFED, are you sure you need to?
Asking because the easiest way for new Infiniband users using CentOS is to just use the included Infiniband packages:
$ sudo yum groupinstall "Infiniband Support"
That installs a bunch of drivers for Infiniband adapters (including most/all Mellanox cards), and things should "just work".
My understanding (might be incomplete) is that Mellanox OFED is more optimised/better for some stuff. But, if you don't need that "some stuff", why make things more complicated?
If you do need to use Mellanox OFED later on, you can remove the inbuilt CentOS Infiniband packages pretty easily:
$ sudo yum groupremove "Infiniband Support"
Hopefully that's helpful.
(note - edited for typo fixes)