Memtest error when OC

Hello. I have a weird problem here. I am trying to overclock both my CPU and my Rams I guess but I can't get it stable. My i7 950 cpu seems to work fine @3,8Ghz but I get a Fatal error in Prime95 which is supposed to be a RAM failure. And this is true, since I am also getting errors in Memtest. I am although not getting errors in memtest at stock ratings which seems weird to me, so I figured I would try and get help. I set the timings manually to 9-9-9-24 at a volt of 1.65V. The frequency is at 1440Mhz or so, I am not 100% sure. My cpu is running at 21x180

System specs:
i7 950
Asus Sabertooth x58
Corsair 12GB(2x6GB) XMS3 DDR3 1600mhz CL9