When measuring the voltages, have you attached a load to atleast the +5V supply? To that power-supply it might be wise not to use the A2000 motherboard as a load, use two of those 21W 12V lightbulbs often used for the break-lights in a car, or some other appropriate load that wont be damaged. That will give you a load of about (21 + 21)/12 = 3.5A on the 5V line (assuming they are linear) which should be enough.
/Patrik
