Make sure all power connectors on the motherboard AND video card are plugged in.

Also, you may want to check the DFI Support Forums and see what suggested memory they have. The last time I'd seen, Kingston wasn't something they were recommending, and that could be a problem.

Additionally, what model is your power supply? 500W should be enough, but if it doesn't offer at least 30A on the +12V rail or combination of, it might not have the juice to run. Still, double check the power connections, as I suspect that.