id say your problem is most likely not enough airflow in your case, or too high ambient temp, or poor heatsink installation. get some case fans to suck the hot air out and replace the cpu heatsink and thermal paste with something better. Hard drive speed would be a more likely cause of freezes and halts, along with a faulty component possibly.
I think is the cooler like funguseater said, because all the disk are Sata II 7200 rpm and had been using them on other config without a problem. So, waiting for the new FX-8350 is not worth and better change the cooler (cheaper!). Thanx to everyone answering, sometimes you miss the essentials.