When i built my first gaming rig i took the best motherboard for the price (80 euros), the Asrock Z77 Pro3.
Its a great board in terms of features and its supposed to be stable, however, i tried overclocking my i5 2500k to 4,0Ghz and it couldnt keep it stable, not under any voltage or Ghz, however, i thought there was something wrong on my part. But since i got it i have been getting random crashes every now and then until a week ago. Then it crashed, and would start up again! I didnt even overclock!
So i RMA'd it and got a new one, after a week. So i took out a different motherboard (some MSI military class board) and i suddenly stopped having these crashes, i could get a stable overclock, hell i could even slightly move my case3 without crashing my pc (this really happened)! So yeah i got a new board and most of the problems were gone, but it took 2 weeks on Asrocks part and i still have random crashes every few days.
Sounds like an issue I had with an ECS GF8200A motherboard I used to use (this was a LONG while back)
The SATA ports fell off the board, then the Sempron 140 I was using in it exploded (litterally, boom, as in fire). ECS Customer support refused to refund, as well as tigerdirect, and could not get RMA. I did not overclock. Not even in the slightest...or flash the BIOS. Worst customer suport service ever.
Well thats what i thought, so i tried it out on a couple different motherboards, and all my problems are completely gone, howver this motherboard of course isnt a high end motherboard, only 75 euros so that might be it, i did expect more of it though, and with good reason.
Even so, each CPU (even ones from the same series) all will have different overclocking abilities. I have heard this referred to as the "silicon lottery" many times.