right, i noticed the beeps are different with connected usb devices. As these beeps happen during active screen, it is without worry.
Manual says:
The following table lists POST error beep codes. Prior to system video initialization, the BIOS
uses these beep codes to inform users of error conditions.
In the meantime i updated bios, was quite old (2008 i think)
Have to see if it still hangs on bootup.
Edit:
This is what i found with new BIOS
http://abload.de/img/p21007134fs09.jpg
I replaced now PSU and will test again. I have impression that the problems are more likely on cold system, not when it runs a while.
