Help needed with FX4100 quad core

hi guys, basicly im abit of a novice when it comes to over clocking. been teaching my self for a few weeks learnt a decent ammount, only thing is,

im running amd fx bulldozer 4100 quad core
78lmt s2p mother board
radeon hd 5500 gpu
corsair 600 psu .
i have managed to clock it my self to 4Ghz. Done this using the multi in the bois. im looking to get it to over 4.5
at 4Ghz on stress test with prime 95 it sits at 27c. havent changed any of the power out puts as the mother board is set to auto with the power.



only thing is, i keep getting a single core faliure and im not sure how to fix it. as im running a stress test right now? core 1,2,3 and 4 have all ran fine for 23 mins. core 4 has come up with this during the test.
[nov14 10.35] FATAL ERROR: Round was 0.5. expected less than 0.4
[nov14 10.35]Hardware failur detected, consult stress.txt file.
[nov14 10.35} torture test completed 12 times in 23 mins- 1 error 0 warnings
worker stopped.

im not sure what is causing it to be unstable but, even after the core has done this the pc is still running ( typing this as the pc is stress testing the other 3 cores still0
so can any one help me get this sorted and to get the cores up to 4.5 ghz or more.
the case temps are realy good so cooling isnt an issue so far  
thanks in advance for any help with this.