Your motherboard is an XFX MB-750I-72P9 - good to put it that way to make it easier for others to help. I like the idea of it being Sly though!
Definitely increase the voltage to 2.2V.
I'm taking back all the nice things I said in another thread about XFX's manuals. This one is lousy, at least the explantion about what slots to use. The diagram makes no sense at all. I do love their MoBo Guide though, everyone needs a copy of this thing. Actually teaches you how to assemble your system without a case, using the motherboard box, anti-static sleeve, etc... Of course, gotta register at the XFX site to get it! LOL
Heck, I know what this diagram is supposed to be saying and still can't figure it out. Aren't 3 of these diagrams identical? And isn't Channel A one green slot and one black slot? Dual-Channel is having one pair in the green slots? ie, dual channel is one stick in Channel A and one in Channel B?
http://home.roadrunner.com/~expertpc/toms/xfxslots.jpg
Put your RAM in the 1st and 3rd slots. That should take care of the problem. The dual-channel "pairs" always go in the same color. I think that will be Green slots. Ignore what the manual says - Pair A should go in Green, Pair B should go in Black.
Good luck. I'll leave you with one more pic from that manual - I may set this up in my Sig or Icon!!! Not sure if this is REALLY BIG RAM or a really small technician! Ya think XFX is employing some of those Oompa-Loompas that Willy Wonka made famous? I love it!
http://home.roadrunner.com/~expertpc/toms/handsonram.jpg