GA-Z77X-D3H not working with dual channel

one of your ram sticks might be faulty. try putting the good ram stick in slots 3 and 4 to see if that works. you can also use memtest bootable program to test your ram for errors

I did try to swap the ram and tried every slot with each stick solo. Nothing. Both sticks work by themselves in slot 4, and both work together in either configuration of 3/4.

Well that motherboard normally supports up to DDR3-1600 RAM. I know usually they will clock down but perhaps there is a timing issue with these. You could try some 1600 RAM and see if the errors stop. If they don't perhaps the RAM sockets are bad. I don't see your RAM on the approved Memory list. I do see some 1866 8GB listed but not your model.

http://download.gigabyte.us/FileList/Memory/mb_memory_g...

Yeah, I was wondering if that would have been an issue. It shows that it clocks at 1866 and even shows all 16GB which is why it is extra frustrating. I just am not sure why the Dual Channel part would be messed up. I'll see if I can find a 1600 or lower stick that I can test my PC with.

G.Skill Ripjaw 2x8GB 1866mhz, and the model number?
Already in the latest bios?

I'll update the specs:
Mobo - Gigabyte GA-Z77X D3H(just updated to 17f bios, no luck)
Ram - G.Skill Ripjaw 2x8GB 1866mhz ram (F3-1866C9D-16GXM)
CPU - intel 3570
GPU - Gigabyte HD7970

Anyways, I got home late so I haven't run the memtest yet. I did flash the bios though to the beta version and it gave me a few more memory options, but no luck. I checked the voltage and it is at 1.5 as it should be. Additionally after flashing bios and all I made sure to try EVERY configuration again with no luck with anything but the combo 3/4 slots.

I have done a lot of google research on it and haven't come up with anything definitive, but I'm starting to think it is probably a faulty board.

You can download a newer bios here; http://forums.tweaktown.com/gigabyte/28441-gigabyte-lat...
It may help you & don't forget to check very closely the CPU pins under the CPU. If you have never done this before make sure you have a high mag magnifying glass, those pins are tiny...really. Look for any bent, misaligned or missing pins. Good luck.

I Had the same issue I have a GA-Z77X-UD3H gigabyte motherboard with 32GB of RAM. Every time I plugged all 4 8GB sticks in I would get Error 15 then 51 my system fans (case and mobo) would run for about 5-10 sec. then restart. I never had anything show up on my monitor just that error on my mobo. After trying the slots in different patterns (1 & 3, 2 & 4, 1 & 2, exc...) I finally had success by plugging into the last 2 farthest right slots (DDR_3_1 & DDR3_3). After the system booted i tried installed windows and played with my 16GB RAM system, I shut down and installed 1 stick in the 2nd slot from the right (DDR3_2) tried starting the system and got the same error. I installed the other stick into the 1st slot (at this point all 4 are installed) and still got the error. i swapped the sticks around, sitll same error. I removed the ram from the first 2 slots and the system started fine. so come to find out slots 1 & 2 (Labeled DDR3_4 and DDR3_2) are channel A. I got ahold of gigabyte Tech Support. They said that RAM should be plug and play. I should remove the motherboard and test outside of the case to be sure it wasn't shorting out (I did and still same error 15 then 51). Next they said to try to re-seat the CPU maybe it isn't seated right (I did that too with a fresh coat of thermal paste. still the same error). Lastly They said that my motherboard must be faulty. Today I exchanged my motherboard for a new one (same motherboard). I installed everything the same way (including all 32GB of RAM) and my computer fired right up no errors. I checked my system info and sure enough I have 32GB of RAM. So my though on your error is your channel A is faulty and to fix your mobo needs replaced