PC boot after off again immediately

Hello

I installed on my intel D945GCLF2 Ubutu 12:04 .
Once I turn off the computer , he shuts down and after 2-3 sec . high again.
Have already a 2nd Board attempts with Mesa on PCI without power supplies exchanged Bios settings rumprobiert helps everything nix .................
Have now Linux CNC 2.7 draufgetan .
Then s worked quite normal shutdown with .
Next day turned off booted again
Thereupon, I thought maybe something with m BIOS the small button cell from the motherboard out pauses briefly in again .See then shuts down normally and remains off .
Two days later the same sch ..... simply starts up again .
Have everything on WAKE turned off in the BIOS .

Another idea ???

I dont know if its related but I have a Atom MB that does this
It does it after you have power cycled via the power button 256 times
(probably a 8 bit bug in the power ucontroller)
its fixed (for a while) by a hard power cycle (switching off the ATX power supply)

Hello
now times awarded Have a Manager password for BIOS did not help .
Belief that the list of information that my be displayed is the black background and white font longer " runterfahren decent " when .
By contrast, if he shuts down and right back up the list is shorter .
Become the next HDD . Try hard disk .
Currently I have a mini SSD 32gb NoName and I read somewhere once that since made ​​problems the hard disk driver and therefore the PC was restarted .

At my other CNC milling machine the same Intel board is only with a 12V Pico PSU and HDD hard drive works without problems .

Here I have a 24V Pico PSU from China and a SSD hard drive with 32Gb
Although I can rule the Pico da he restarts with a normal PC power supply .