Hello Robert,
What driver version were you using on Xenserver 6.2 SP1 ? If you recompiled before on Xenserver 6.2, you will need to do it again on Xenserver 6.5 SP1.
Xenserver has Supplemental Pack guide. See chapter 5 than chapter 4.
Mellanox EN drivers URL: http://www.mellanox.com/page/software_overview_eth
Cheers,
~Rage