First off what are you using for cooling? and for that frequency use 1.425 volts and then see what you can reduce it to, with alot of cheaper boards thats the minimum voltage i could get away with, auto did not select the proper voltage. Make sure you have turbo and IO-C state support turned off when overclocking amd processor. Also if you want so more preformance boost look into increasing you NB and your HT for even more preformance.
I currently have a phenom 2x6 1100t at 4.0ghz with 2600nb and 2600ht, 28 degrees celcius idle , with a corsair h70 cooler and my cpu voltage is at 1.425 becuase my Asrock 880gmh wont let me get away with a lower voltage