I have installed components from an old box into a new one. Replaced the mother board, added a graphics card, and transferred everything else. It's all hooked up, no grounding to the case is found, thought it was good to go. Powered up the rig, it turns on and all fans and LEDs turn on, then it turns off ten seconds later. Like I said, I checked grounding, the wiring, the mobo setup, everything I could think of. Never had this problem in my other rigs, so I'm banging my head into a wall to figure it out. Oh, and it keeps up the power on/power off sequence, with about ten seconds to both on and off.
MSI 7519 VER 1 mobo
Nvidia 9400 GT
Intel Dual Core (don't remember which exactly)