Did you go from 32 bit to 64 bit OS's? As 64 bit tends to stress the cpu a bit more with more complex instructions, whilst speeding the system up can cause an overclock to become unstable. Looks like you might need to raise the cpu voltage a bit, so try that first. I think 1.3V will be plenty, and people generally recommend to stay under 1.3625V (load voltage). What does cpu-z say as the voltage when booted up? And what does it drop to when you load it?
When overclocking the cpu and ram no extra stress is on the southbridge, so I do not think it is that.