Sun,
How many 6 pin power connectors are required for that video card?
I suspect TWO.
From LOTS of things I have read in the past about these high end video cards, they do require lots of readily available power, a minimum of 50 amps on the power supply which on many 500 - 600 watt supplies is lacking.
It is the AMPS on the 12 volt rails that count, not the wattage rating of the power supply.
I can't stress that enough.
This is why I look for multiple 12 Volt RAIL supplies with over 60 total amps readily available and at least 25 amps on a single rail.
2. Try that new card in a different computer if you can. MAYBE its the pci x 16 slot.????
The 750 watt power supply was a good idea assuming it has some good 12 volt amp ratings.
Keep us posted.
micro...