So I took the MLNX_OFED_LINUX-1.5.3-4.0.42-rhel5.5-x86_64.iso and used the mlnx_add_kernel_support.sh to create an iso for RHEL 5.3.
Seems to be working quite O.K for now.
Now the next step is to get good nfs performance through these cards on a server :-)
Thank you for your reply.
One more thing under the "Supported HCAs" section of the OFED 1.5.2 release notes, Connect-X IB is listed as a supported HCA but there is no explicit mention of Connect-X 3, will it still work ?