For future reference, you should list temps as celcius.
So I'm going to make this analogy of how I understand it, if I'm wrong anyone, please please correct me.
Overclocking is like lifting weights. Setting it to 4.0 ghz without altering voltage (or not enough) is like giving a 13 year old a 400 pound bar to bench. He's not going to be able to even raise it, thus it crashes. If he were given steroids (More voltage) he would be able to handle more weight than usual. Certain people (CPUs) simply cannot lift a certain amount of weight, no matter how much steroids they use. However sometimes the bar itself (Motherboard) just wont hold up as much weight and will break. (Clockblock)
So more seriously since I was kind of confused by that since I'm a technical guy, basically your clock was too high. If you're going to overclock, you need to mess with both voltage and the core clock. Don't use OC tools in the OS as they are not as stable as overclocking in the bios, plus it uses system resources to change the settings. (And you overclock to get more out of your system, why tax it by making your computer work harder just so it can work harder?)
Changing the settings in your bios isn't permanent, it's just what speeds your computer boots from. If you overclock too high, your computer just restarts and tells you that your overclocking messed up and to back in the bios and change it.
After you change your clocks, run Prime95 for about 5 minutes (or longer. Longer the better.) and run Furmark or MSI Kombuster. In my experience, furmark and MSI crash my computer faster than prime does. (No gpu overclock) Running these will tell you if your system will be stable. You don't want to skip out on these tests and have your computer crash in a game of Starcraft or in whatever game you may be playing at the time.
- The 5 minutes is only for gradual overclocking. During the final overclocking speed, you should have it running for at least 30 minutes to an hour. Many people leave it on overnight. Again, for the reason in the previous paragraph.
edit - About the motherboard comment, it's not a common (at least from what I know) clock block. Usually it's temps and the CPU itself. In my case however, it's my mobos chipset that's clock blocking my cpu, htt, nb and gpu clocks.
