David,
Some of the first Asus P58 board's were shipped with the wrong Intel chipset which resulted in a ton of different problems. Seems you got one of them. Check with the Asus site and see if they have any updates for the board to include the bios.
That EVGA 8800 GTS should be a solid performer. The box I am using now has two of them installed. Make sure that the power plug is in fact using a 6 pin connector and not a 4 pin. Maybe remove and reset the board to make sure it is fully set.
Your memory requires a 1.9v which should be no problem as that board will run on 1.8v to 2.0v. Check though that it is set to at least 1.9v and your timing is either 5-5-5 or 6-6-6. You may also want to have your local shop test those chips. Alternately you can download this Microsoft program and test it yourself:
Memory Test
Check the fan on the CPU - faulty fan with overheating can do weird things.
Can't think of much else at the moment -
Ron