Intel® Core™ i5 Processor I5-750 - SLBLC
I thnk you are hitting the volatge range for the chip, so be careful on pressing it. I know you got that error previous to upping the voltage, but I wouldn't press it.
Here is another good description of OCing the i5-750 :
Feature - Overclocking Intel's Core i5 750 | bit-tech.net
If you increase your voltage your gonna start seeing increased temps. If you are on a stock cooler HSF then I would not go higher and as the article above states, 1.45-150 is needed to get more at 200mhz base clock.
Another concern is the error on the worker #3
The third core in your screenshot Worker #3 had the same issue in your last thread. I think there is a way to disable cores for testing, but haven't done it. I think this is in the BIOS. you might have a CPU that unfortunately is hitting a wall on that 3rd core. none of the other ones are showing errors right?