Re: RAM only recognized sometimes
I'm thinking this may have something to do with the memory being used. Most of the memory available right now is rated for 1.65v, this was fine for the older i3, i5 and i7 cpu's as the integrated memory controller worked at 1.15 volts (the DRAM Voltage needs to be within .5 volts of the Integrated Memory Controller Voltage).
1.65 - 1.15 = .5
The Memory Controller on the new Sandy Bridge based cpu's is 1.05v.
1.65 - 1.05 = .6
.6 is out of spec.'s
If your having problems it could be the memory controller having difficulties running out of specifications. I would try raising the Integrated Memory Controller Voltage to 1.15 volts. In your system bios the Integrated Memory Controller Voltage is called the VCCIO Voltage.
I just bought a 8GB (2x4GB) set of Corsair Vengeance DDR3 1600 8-8-8-24 @ 1.5v and I'm not having any problems.