Ram problem? or something else?

So I've been plagued by blue screens with kernel power 41 event/task 63. I've researched and none of the supposed causes have helped my situation. I recently started playing with the ram. With only one stick in it will not boot in slots 1 , but will boot with in slot 2. seems that as soon as I put in another 2gig of ram (same brand Mushkin) no matter what slot, it starts rebooting or freezing with sound loops. I have only one stick in currently in slot 2 and going to leave it on see how it fairs, if it works I may just go get one 4g stick to put there to essentially jerry rig it, but is this sign of bad mobo?

amd pheno x6 1055
gigabyte 770t usb3
radeon 5700 series
650 watt power
1tb hitachi hdd
kingston 30g ssd

Wierdest part is all of this started when I replaced the video card(properly installed drivers), but cannot say that is the issue becuase ive tried the old ati card, and a nvidia card and still experienced same issue. I am starting to think that my mobo memory rails are failing, because memtest would come back clean sometimes and errors others depending on what slots they were in.