I would say it is probably voltages. I would check some reviews on that motherboard and C2D cpu in general and get some recommendations on where to set them, but auto wont work for much more than a 10-25 percent overclock. I'm pretty sure your vcore is too low at the very least. But as far as where to set it, that will be a trial and error solution at best. They are all different.
You need to be really careful as you are raising voltages and keep an eye on temps.
The one other thing I would check is your GPU temp. Those will throttle if they get too hot and sometimes you just wont know they are doing it except that things slow way down.
EDIT it may also be memory voltage. That memory needs at least 2.2v and you have it set on auto. That is a problem for sure.