Help me stabilize my OC, some peculiar things happening here...

Got my i5 running at 4.7 GHz at offset +0.050 (leading to a vcore of 1.344 under load in CPUz). It is OCCT CPU test stable for 3 hours and prime95 stable (small FFTs). My RAM is rated at 1600 9 9 9 24 @ 1.5V. I set it manually and run 3 memtest intstances, 0 errors after 100% coverage,

NOW; I run prime BLEND test and after like an hour I BSOD. What should I exactly do now? RAM alone: stable, CPU alone: stable, RAM+CPU load: unstable. I bumped the offset to 0.055 and prime blend again BSOD'ed. I'm beginning to think its not vcore related.
.. should I bump the VCCIO?

BIOS settings for CPU are:

Everything is default except
multi = 47
offset = + 0.05
Duty Cycle = 350
Spread SPectrum = disabled

Assume that you have the k version. Try lower your RAM frequency. I5k only supports 1066mhz and 1333mhz memory.

http://ark.intel.com/products/5221 [...] -3_30-GHz)

No, it isn't.

Generally, -1600 RAM will work. Anything higher may or may not work. And even when it does work, you will gain very little extra performance. And the price will be increased instability in the memory subsystem.

The blend test failure indicates that you have problems with your memory settings.

If you are trying to overclock your memory, reset the RAM speed to 1333 MHz. Test the stability with the blend or large FFT's test. If it is stable for however long you feel you need to test, increase the RAM speed to 1600 and repeat. If you feel the need, continue testing higher speeds.

How long to stress test is always a personal call. My goal is 24 hours on both small fft's and blend with EIST enabled.

noob question, is upping the memory from 1333 to 1600 OCing?

im looking to get i5 and was told get 1600 RAM, but i also see that when installed it will default back to 1333.

any adverse effects of doing so?