Probably just unstable.
A 30% overclock is quite a bit. I'm assuming you didn't change the vCore (voltage going to the cpu) ?
When you run a cpu faster than what it's intended for, you usually have to give it a bit more juice.
There's always the possibility you've reached the limit for the cpu as well.
Try to find the max overclock for your cpu, keep increasing the overclock slowly until you find the last point at which it'll boot.
I haven't used that util so I don't know how it works. Are you running a divider on your memory or does it do that automatically? If it doesn't and you aren't, the RAM may be trying to run too fast for it's own good.

I think 3Ghz is fast enough for now! 1.68V on the CPU voltage is not healthy. Granted, it works fine now, but too much juice can gradually kill a CPU. Your results might vary, but to be safe I would just sit on default speeds - 3Ghz is more than enough for general usage and great for games.

If you really want to overclock, then stay below 1.6V, and see how far that gets you. Also, what speed is your RAM running at? You can check with a utility like CPU-Z.