As a first thought, are you sure you need the Mellanox OFED stack?
The yum "Infiniband Support" group included with standard RHEL 6.4 should "just work":
$ sudo yum groupinstall "Infiniband Support"
Apparently it's not as optimised for stuff as Mellanox OFED, but if you just need something that works "right out of the box" it's a good option.
Hopefully that's useful info.
(note - edited for minor clarification fixes)