if your not overclocked and your cpu voltage is 1.4+ for stock that could be the problem. normal range for harpertown is .85 to 1.35v, only overclocked is when it should be higher. now the older cpu's from "core 2" era had voltage as readable, could temp would display that voltage. sometimes though it does display actual voltage and i do believe it based on motherboard and certain cpus possibly not desktop core 2 parts.
i think what is confusing me and possibly others is you went from no overclocking to now overclocking it. if your running blend it uses both cpu and ram, but when making sure the cpu is stable. you need to follow my other post and make sure it will tax all cores with the largest size set to L2 size. as running blend will not fully test the cpu it will off load at some point to the IMC/ram. you really need to run prime95 longer then 2 hrs, as it will not go through all the cache size the cpu has in that short a time frame. once you narrow down its not the cpu then we need to check ram then. it the cpu foes fail in prime95 then small voltage steps up.
The voltage and everything else except usb keyboard and mouse functionality was on optimized defaults on the previous bios file. Next time I run Prime95 I'll check the settings you mentioned. One thing I noticed is the motherboard Vcore setting and the maximum CPU vcore Open Hardware Monitor reads do not match. I've set CPU vcore to 1.45 in bios but Open Hardware Monitor reads a maximum CPU Vcore of 1.408. Shall I use a CPU Vcore setting in the bios that is no more than 1.45 or shall I use a CPU Vcore that's not read above 1.45 on a monitoring software ?