If its possible / cheap - I always suggest going with better CPU cooling, and those temps are high but I'm not going to be like "**** halt everything" kinda high. Sometimes, and I know this sucks -- things start to wear... Your CPU might be getting old and needs a bit more juice to hit that clock... Your motherboard might be getting a bit worn too.
Im going to agree with everything said previously (but I'm saying it - so it gets an extra
- one more voice agreeing with the crowd isn't a bad thing!): Raise voltage a tad - keep an eye on temps - and even if your one stress test tool causes crashes - if every single other thing you do is stable - I dont see a problem. Purists will say "its not stable unless its ALWAYS stable" - Ayekalooter says if it works day to day for what you do, don't sweat the details!
Good luck getting your issue sorted out, and let us know how it turns out -- Im sure Im not the only one watching this to see what happens!