Strange graphics glitch, solved by lowering ram clock speed?

hey everyone!

since this does have to do with overclocking (well a little) i thought this would be the best place to put this thread.

well firstly my system-

amd athlon II x2 255, 3.1ghz (1.440v according to cpuz)
8gb of corsair vengance 1.5v,1600ghz ddr3 ram (2x 4gb sticks, underclocked to 1333, running in dual mode)
Asrock - M3n78D motherboard
corsair gs600, 600w psu
kfa2 - geforce 550ti 1gb

the problem -

i first noticed this when playing on assassins creed brotherhood, and the problem carried on to revelations
where at a random time, one texture would cover the entire playing screen and all i could see would be that, and the hud. after an alt+tab to the desktop and back into the game again, it would be fine but it was occuring frequently.. same thing in revelations..

i pondered on it being a glitch in the game, but after considering that id only just upgraded my ram a few weeks ago
and i had a fair bit of system instability untill i got the ram settings in the bios set to the correct settings (1.5v and 1600mhz)

so everything seemed to be ok the odd crash or bsod but i just dismissed it untill now..

i dont know why but for some reason i developed the thinking that maybe my psu was unable to cope properly
with the new ram and after looking up reasons for a bsod i figured ill pop into the bios and drop down the ram clock speed to 1333ghz just to see.

low and behold i sat on assassins creed revelations for an hour and a half without one single crash, bsod, or texture covering the screen error

and last night i was on for 2 and a half hours and again , solid as a rock, not one crash

the question -

im a total noob when it comes to overclocking, the reason being is that i dont really like to, im a bit fearful of doing it as i dont wanna mess anything up

but with the OC ram (being 1600ghz) would i have had to OC my cpu to match the new overclocked ram? or should the ram be ok running at its overclocked settings with out OC'ing the cpu?

and also, from my specs IS my psu ok for my system specs?

im fine with building a system, but its the voltages, amps, OC'ing, memory timings kind of things that im not up to scratch on as i said before im not really into overclocking, but is my fear causing me to miss out?

any help, advice and opinions are welcome!

Thanks!

no one? anyone??