Adding another two CM2X1024-6400 sticks causes problems

[tehsea]

So i decided to upgrade to 4gb, so I got another two sticks of CM2X1024-6400 (it may be of interest that the old sticks are 5-5-5-12, which didn't seem to be available, otherwise I'd have gotten those). Fwiw, the old sticks are 1.9V ver 5.2, the new also 1.9 ver 7.2.

 

Anyway, just plugged them in and they worked fine for a couple of long relatively memory intense sessions, to just freeze the system mid use. Then to not being able to boot. Removing the two added sticks allowed me to rebbot, and yet to have any problems.

 

So I should probably set something up in bios, but need some guidance here.

 

Thanks in advance

[RAM GUY]

With 4 modules I would suggest setting the memory frequency at DDR667 and set the memory Voltage to 2.0 Volts and set the NB/MCH/SPP Voltage to +.2 Volts as well and test the system with http://www.memtest.org. In addition, with some MB's (Mostly ASUS) you have to disable legacy USB in the bios when running any memory test.