HD3870 Power trouble

Recently a bought a visiontek hd3870 video card. My problems start after i shutdown my computer with the card installed in the PCIe slot of my motherboard ( for reference my motherboard is a Gigabyte GA-965P-DS3 rev 2)

here is what happens. I seat the car and boot the machine, everything is fine. Once the machine is up I can reboot it and everything comes up great. The problem starts when i shutdown the machine. After a shutdown when i restart the video card keeps telling me that the power is not hooked up properly. this happens every time that i shutdown and start it back up. If i then re-seat the card it will boot perfectly until i shutdown and then on restart i get the power message all over again.

any ideas? i am runnnig the latest bios and chipset drivers for the motherboard and the latest drivers for the video card. also i have a 750W power supply so that should have enough power for this card but there could be something going on there too. i am completely lost on this and would love to hear any suggestions. My OS is XP Pro. but i don't think this is an OS issue.

thanks for the help!

yes this prevents windows from loading. this message will post before the gigabyte bios splash screen when it does post. there is not error message for this because it is the the normal message you get when no power is attached. if i reseat the card and then stat the machine i can get it into windows. once in windows i can reboot all i want. once shutdown then i have to reseat the card or everytime i boot i will get message to check to make sure my power is connected properly.

i have tried the card on another mobo and get the same results. i even returned the originally video card I got and tried a new one on both mobos but still the same error. it almost seems like a psu issue but that wouldn't explain why it doesn't work unless re-seated so i kind of ruled that out.

i will try the "push test" when i get home from my business trip this weekend.
i will also try the slot X1 idea.

i have had another PCIe card on this mobo, i am replacing my ATI x850xt PE card with this HD3870

thanks for the thoughts! i will let you know the results of the 2 tests this weekend.

the psu is a cool master real power pro 750W model number RS-750-ACAA-A1, it says it is compliant with ATX 12V v2.3 and EPS 12V v2.91 standards, not sure what that is really.

it also says that it is rated for 19A on each of the 3 +12V rails. at this time i do not have another psu big enough to power this card. last decent psu i had popped which is why i got this new 750W.

the PSU is only about 2-3 months old so it is still pretty new.