Problem with 890fx chipet and 16gb of ram

Hi guys.

Not been on her for a very long time, so hello to anybody who remembers me :D
If you need any help overclocking socket A or soldering (I doubt many of you guys do that any more :P ) im your man.

Not been doing any proper overclocking for ages but ive recently run into a problem and i wanted some advice.

I have a Asus M4A89TD PRO (890fx chipset) and was running 4gig of Gskill for ages but decided to upgrade to 16gb a few months ago.

Since installing the new ram which is Crucial BLT2CP8G3D1608DT1TX0CEU, 16gb in two 8gb sticks CL8 1600
I had some occasional instability which I put down to my overclock but the last few weeks its been worse and I had some HDD corruption so I thought I better try and fix it.

Got rid of the overclock, dropped the memory timings down, then underclocked the ram, tried changing vmem but still had pretty much identical problems.

I went back to my Gskill and everything is now fine, even overclocked its running stable again. I even ran prime95 and superPI.

So all I really wanted to know is there anything I should setup when running 16gb on the 890fx chipset? TBH there are settings for memory timings in the BIOS I dont understand any more, im out of the loop :)

Did I do the wrong thing getting two 8gb sticks rather than 4 4gb sticks?

I might just have a duff stick of ram but I wanted to make sure I've not done anything dumb before I bother Crucial's RMA department.
Don't assume I know what im doing I may have missed something obvious.

Thanks for any help :D

Have tried bumping the nb volts up (AMD IMC) that's what I had to do to get 4x4GB of single sided stable on the MSI 890FX.