4770K overclock to 4.5GHz

1) if it's only OCCT then perhaps you are fine. I have had Prime95 give errors when everything else says I'm fine, and I've seen no issues in several years (until Windows 10 for a few months but that's not a hardware issue)

2) also try the Intel CPU diagnostic tool from Intel site:
*The Intel tool sets my i7-3770K back to 3.5GHz with no Turbo though so it's almost useless. Not sure if it does that for everybody or not.

3) MEMORY-> it's not clear if you've also overclocked your memory as that may explain your issues. I usually avoid overclocking memory. If you haven't done so run Memtest86 for a full pass or until errors.

www.memtest86.com (may need to change BIOS boot order to boot from DVD/USB)

4) CPU voltages:
I would keep this as low as possible while still being stable.

5) According to this GUIDE only about 70% of the chips were getting to 4.5GHz so if it's a CPU problem then it could simply be silicon lottery:
http://www.overclockersclub.com/guides/overclock_intel_4770k_guide/

Reasons you can't overclock higher include:
a) silicon lottery
b) temperature
c) motherboard (Voltage stability from VRMs)
d) Power Supply (if Vdroop too much for VRMs to compensate)

I'm guessing silicon lottery is your main issue.

6) Can you get to 4.3 or 4.4GHz?
If so, why not just stay there? (and possibly adjust Turbo values as per below)

FYI, the difference between 4.3 and 4.5GHz is 4.6% at best, and often there's NO difference observable. It's fun to tweak, but maybe just make it STABLE and forget about it for a while.

7) TURBO values:
I have an i7-3770K so this may or may not apply, however I can adjust the frequency (through the MULTIPLIER) for each of my Turbo values. I have four; one for 1,2,3,4 core loading though I don't know how the PC decides the load level.

Example:
a) I was overclocked to 4.3GHz (no voltage changed), however my Turbo under full load was 3.96GHz.

b) I then manually changed the Multipliers only and the final values that were stable were 43, 43, 42, 42 (under heavy/full load my actual number reported in Task Manager is 4.16GHz).

*Every CPU is different. Motherboards are different in overclocking options too, but for some this may be the best option.

So maybe max to 4.4GHz, and if possible manually adjust the turbo values.

7) Overclocking utilities?
a) BIOS quick
b) Motherboard software for Windows
c) Intel XTU for Windows (Extreme Tuning Utility)