my xbox would frag on and off. I didn't know what caused it, but sometimes it would frag, and sometimes it would work. Long story short, it turns out the female connector for the power plug had loose traces, and they were causing it to frag randomly (or rather, when the power plug wasn't positioned corrently). two little dabs of solder later and it's right as rain. This may or may not be your problem, but the fact that it's 'tempermental' suggested to me that you would like you know this.