Did you use LLC? Most of us who overclock with the ASUS P8P67/P8Z68 series use LLC at Ultra High. If so, Load Volts will be higher for IBT/AVX VS Prime95.
So If you're not using any LLC setting, or a very low one, the opposite could happen, and make IBT/AVX unstable. Even if this was true, your computer would never crash in anything else, as long as you where Blend stable. This is because nothing else, except IBT/AVX would drop Load Vcore lower than Blend.
LLC is disabled because of the sleep/resume issue. Until they fix that I won't enable LLC, unless there's another fix.
My Blend test was 12+hrs stable, but still crashed when encoding. It also crashed after 1 IBT run.