You really should consider using your BIOS to overclock. Windows based overclocking software does not offer as many options to achieve your maximum overclock.
It sounds like you have selected a higher overclock setting than your system can even boot with. My guess is that you will need to increase your CPU voltage to be stable. You need to overclock in small increments and test for system stability, and monitor your temperatures.
You need to research the maximum CPU voltage, maximum northbridge voltage, and maximum RAM voltage. and most importantly maximum temperatures for these. Remember that increase in voltage equals increase in heat.
There are many guides here at Tom's to help you learn and UNDERSTAND how to properly overclocking your system. If you are interested only in a marginal overclock, the OS based overclocking is OK to use. If you want to spend the time to find the true "sweet spot" of your system, where you know that you have found the optimal overclock based on benchmarks, temperature monitoring, and stability test, then OS based overclocking is not the way to go.
There are quite a few video on youtube for AMD overdrive, I suggest you search there.