I don't see how it could be a frequency problem. But if it is, I'm not the person to ask since my knowledge of that kinda stuff is pretty low! - You may have to wait for someone else to stumble across this post.
Thinking about it, this could be an over-heating issue. Download and install
Speedfan, and see what kind of temperatures it says you are getting. Keep the software running and the next time your computer hangs, see if the temperature is any higher.