ip 35 pro boot problem after oc

[rlsf]

hi,
i bought my rig about a month and a half ago, it's all in my profile but the main parts are:
E4500
IP35 PRO, bios: 16
HD 2900 PRO
2X2GB DDR2-1000 Mushkin
Corsair HX520W

my problem (sorry for the long story, don't want to miss any important information)
when i bought the computer, i overclocked my CPU a bit (to 2.66Ghz, on 250FSB), it worked fine until last month, when my machine would start its boot sequence and stop with post code 7F and my screen would have its power blink in yellow (as if it identified it is connected to something, but not receiving a display signal), i used my warranty and it turned out my video card was faulting, so it was replaced.
i then tried to overclock my machine again, in a different way - 2.66Ghz on 333FSB, it worked fine for two days (i was playing GTA IV during that period).
i turned it off, and on the next day, when i tried to boot my computer i had my screen blink again as if it doesn't have a display signal. This time however my board had its post code at FF, and i could hear my OS loading successfully, it also responded to shutdown through keyboard.
i had to reset my CMOS in order to have my display back again. it seems some part of my system is still faulting, but since it only happened during oc, i'm not sure how can i isolate the problem.

thanks.

[BUFF]

how much do you know about overclocking?
was the fsb the only thing that you changed?

[rlsf]

not too much in practice, read quite a lot about it before giving it a shot.
i changed memory voltage to 2.1 and their timings to 5-5-5-15 as described in their specs.
also changed the divider to allow them running on 1000Mhz.
lowered multiplier to 7 and disabled C1E and EIST.
no other voltages were changed, on my 1st attempt (a year and a half ago) i also did some runs of 3dmark06 + OCCT to verify stability, didn't run them since though.