Same problem, tried SSD without it making a difference for the boot process. Removed all non-essential hardware items (external usb, external audio, video card, DVD-drive, HDD), re-seated memory, dusted, and still could not get passed this issue without resetting CMOS (see below) or letting the power drain in the power supply. Also tried an alternate power-supply without any difference in result.
Resetting CMOS will also get the device to boot with the clock reset. Out of all the pieces involved in the power-on process (power button, power supply, motherboard, and CPU) the cheapest is the power button by far.