Comp sudden BSOD, will only start with one RAM stick

Okay, first of all, here is what I have -

AMD Phenom II X4 955 Black Edition Deneb 3.2GHz
ASUS M4A89GTD Pro Motherboard
MSI R5770 Hawk Radeon HD 5770 1GB
G.SKILL Ripjaws Series 4GB DDR3 1600 (2 x 2GB)
CORSAIR CMPSU-750TX 750W Power Supply

And here is my problem -

This morning my wife turns on the computer, and when she tries to open Firefox, the computer suddenly gets a BSOD, and will no longer turn on.

I get home from work to look at it, and the MemOK LED light on the MB is illuminated (no flashing). The computer, at this point, still will not turn on. I figure it is a problem with the RAM, so I grab an unopened package of RAM (Corsair XMS3 8GB DDR3 1333 2 x 4GB) that I had, and installed it in the computer. It still will not turn on. So, I pull out the stick in slot 3 and try to boot the computer with only one stick in slot 1.

It works. The computer boots up, albeit slowly, and I get to the BIOS screen, where I simply use default settings and get to windows (windows 7 home ed.). However, after several reboots, the system seems extremely unstable, and I often get a BSOD for seemingly unrelated tasks (mostly while accessing the internet).

Now for some history -

I built this rig about 2 years ago, however, about a year ago, my (at the time) one year old son would sneak under the computer desk and rapidly press the power-strip button on and off. Of course, as soon as I found out this was happening, I stopped the behavior, but I suspect the damage had been done, and sure enough, the computer hasn't acted the same ever since (random slow-downs, will not come out of sleep-mode without a hard restart, etc.). I'm sure the computer was subjected to pretty bad power-spikes/surges from being rapidly turned off and on, and I wonder if this has somehow damaged the PSU or motherboard (or both).

Even though I built this computer, I'm still not the most advanced tech guy - can someone help me with this problem? Is there anything I can do to isolate whether it is a bad PSU, Motherboard, or RAM? The MB manual indicates to place the single stick of RAM in slot one, however, I cannot get the G.SKill RAM in that slot because the CPU cooler interferes with it (I can, however, get the Corsair RAM stick in slot one, it is a much smaller stick of RAM) - so, unless I can test the G.Skill ram in another slot other than slot one, I can't boot the computer up with the original RAM (it won't start with two sticks of RAM, as I said earlier...)

Anyway, enough rambling on my part - any help would be VASTLY appreciated - and I thank in advance anyone who takes time to respond - please let me know if there is any other information I can post with. Thanks!