I'm getting the same exact problem with a GA-P35-DS3R. I suspect this is an issue with GigaByte boards that do not report proper PCI-E values back to the software. We need to find out what nVidia is using to make the judgement with its sentinel program. If nTune and EasyTUne are both using the same sensor for the sentinel, that it's obvious we have a motherboard issue on our hands.
I'm using an OCZ Game Xstream 700W PSU with both PCI-E connectors plugged in.
Are you able to run yoru card with either one of the PCI-E connectors? Or does it screech even if one of them is plugged in? I'm trying that now to see if one of the graphic card PCI-E plugs is bad.
Ok i found my problem! Turns out one of the PCI-E plugs on the video card is DEAD. I found this out by plugging in a single of one instead of both, which should work without beeping insanely. When i tried it on first one alone, it worked, no beeps. When i tried the second one alone, it did the crazy wailing beep. As though none of the PCI-E connectors were plugged in. So RMA it is!
I have same problem when i only put 1 connecter in i get a beeping noise
What also strange is the +12V only is 0.77 V but when i look in my mobo bios 12V = OK
And i saw some photo's from other guys and they had same problem but there system worked fine.
So i also think it's a Videocard problem Let me know if you got your new when and if everything is OK now