Thanks for the link xblade. Put in my set up and it says 393w does that seem a little low?
You didn't mention what brand you are using, or where you live. Some areas of the world have dodgy power with lots of brownouts, but usually it's a crappy PSU. You are using well under the recommended 80% of the PSU, so it is either the PSU, or the power going to it.
I would replace it and see what happens.