You either need more vdimm or more vdd. 2.9 isnt always enough believe it or not...not to mention maybe you need to evaluate the timings you are trying to run bud.

If I am not mistaken, on NF2 boards, the ram is getting its juice off the 3.3 rail...you need to have a look at your rails and let us know if they are terribly low or fluctuating alot under load.