Overclocking RAM, trying to figure out how it really works

Hey you guys. It's been a while I've been looking to overclock my computer in general, and I've found I've never bothered about RAM. I've read most of the guides around here, but I still can't figure some things out, mostly how the system reacts when overclocking RAM(as in, why x happens when it's not stable).
I have DDR2 RAm I've been trying to tighten timings on, but I'm not sure how to proceed. My RAM is in my rig details. It's currently @ 800Mhz, 5-5-5-18 @ 1.82V.
I figured as this wasn't not an increase in Mhz, it would not require more voltage(I fear this is wrong though, read on.)
My rig is pretty stable, about 4hrs in Prime95 before I manually set it off(stable enough for me, seems only heat problems arise after this much time, and normal usage, even on heavy gaming, does not scrape the load P95 offers).

I tried to go slowly, but only changing my CAS Latency to 4 from 5, and then rebooting to see if everything was still under control.
It booted normally, I had time to benchmark and see somewhat of a increase in performance. I then tried to boot up P95 to see if I could go on, and within seconds of it starting, Core #1, #3 and #4 failed and I stopped the tests.

Going back to the original timings resulted in stability once more.

I wonder if I should increase voltage; if it's actually worth it to do so and all. Furthermore, I wanted to know if my northbridge speed and timings would work together in offering a better system performance, or if tightening my timings would affect my northbridge overclock in a bad way.

I looked up my RAM and found out it's supposed to run @ 2.2V for 4-4-4-15, so I did just that and it seems stable. 1hr in Prime95 did nothing, what's the difference between using P95 and memtest?

I realized my RAM was badly indetified by EVEREST and all, and that my recommended timings and voltages were actually 4-4-4-15 @ 2.2V. I do not know if I can actually push the speed out of those sticks, I' ll try at some point, though. Is the brand I'm using known for being good overclockers? Do you think I can actually push 1066 out of those?

Thanks for the tip, made a bootable DVD to test my RAM, works wonderfully, and my RAM is stable

But I mentioned my RAM being stable... what were refering at?

Ohhh, okay, I thought there was a misunderstanding
I'm @ the rated settings I found on the OCZ website of 800Mhz with 4-4-4-15 timings @ 2.2V.
Runs fine, the timings have helped my memory benchmarks heh. They passed memtest and all. I'm trying to figure out if pushing 1066(or so) instead or 800Mhz and loosening the timings instead of just tightening them like right now @ 800mhz would be more worth it.