As flakey as it seems, I would look at your power supply and see if it is in spec,
you can download a hardware monitor here http://download.cnet.com/windows/3055-2094_4-10793486.html?&tag=pdl-redir
when you install it be sure and decline the weather app, or you will have another piece of crap running on your system. but run the monitor and you can view information about your hardware real time, you can look at your cpu core voltages and temp and see if something funky is going on.
do you have access to a spare power supply you could swap out for testing?