The biggest problem is different manufactures produce power supplies with different amounts of amps on each voltage. The main ones are 3v,5v, and 12v. On a 400w or 430w PSU if you 5v has 50A then the 12V is going to have a low number of amps.
We don't know what your "New video card" is, but chances are a higher watt power supply would make your problems go away. The specs say your new PSU only has 28A on the 12v supply.
The 400w psu may have more amps on the 12v channel and less on the 5v and therefore it worked.
However to avoid all this non-sense get a 550w or 600w psu and you will have enough amps on all voltages.