Power seems to always be a problem, so that is were I suggest you start looking...
1. use a voltmeter and check voltages going into and out of the M2-ATX
2. check the voltages on your supply lines (12V and 5V)
(if unsure if they look right, post back here what you find)
After that I would:
1. check memory module (have you tried swapping it out?).
Still can't figure it out:
start with just the bare essentials (ie: no usb devices, no firewire, nothing outside the motherboard, cpu, memory, vga cable and keyboard). Make sure that runs stable, if not start looking in detail at the CPU and/or MB....