Hello, I have a problem that is driving me nuts.It's at a point of becoming ridiculous Parts in system; mobo: nForce 780i SLI Part Number: 132-CK-NF78-A1 Intel Core 2 Duo E8500 Processor BX80570E8500 - 3.16GHz, 6MB Cache, 1333MHz FSB, Wolfdale, Dual-Core, Retail, Socket 775 MPN: BX80570E8500 CORSAIR XMS2 DOMINATOR 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel, Model TWIN2X2048-6400C4D GeForce GTX 280 Part Number: 01G-P3-1280-AR power supply: Ultra x4 1200 watt model# ult-ha1200x Only used for testing ( nForce 750i SLI Part Number: 122-YW-E173-TR) ( nvidia 6800 pci-e video card) ( old pci vid card ) let me try to get to the point without making too long a story out of this. Sorry if I chop the story up, because it's been a long ordeal. The problem I'm having is that I cannot get my 780i mobo and the x4 ultra psu to work together. Initially, It started out like this. I started the system out of the case with the mobo on a cardboard box. Connected 1 stick of ram, 1-280 gtx video card, cpu and fan. Hooked up the 24 pin and 8 pin power connectors. The system starts and I'm able to get into Bios. I check the temps ( they are within range, nothing overheating as far as what the temps are reading) check the voltage. the + 12 volt is @ 12.35. and then the system shut down. I restart the system, it goes partway through the codes and shuts down. ( I don't remember what codes it shut down on) Now the system will not start at all. It powers on for a second and then shuts down. I remove the 280 gtx vid card and install a nvidia 6800 video card. Same thing. I remove the 6800 vid card and install a old pci vid card. Same thing. Hook my old thermaltake 850 watt power supply with the 6800 video card, same cpu and ram and it works.( the +12 volt reading was @11.95volts with the 850)( thermaltake 850 watt power supply does not have the 8 pin pci-e connector for the 280 gtx) it powers up and stays on- in bios with no problem. When I use the x4, regardless of ram or video card I use, it will not boot. Lost yet? Now.....It gets better. I I have a nForce 750i SLI Part Number: 122-YW-E173-TR motherboard. I connect the x4, 280 gtx vid card, 1 stick of ram and the system boots up fine, no problem. So basically I swapped the components from the 780i to the 750i. ( every part I used I is listed at the beginning of the post) This is the second 780i motherboard within the last three weeks. (The first 780i was a replacement for a 680i that went bad, another story) when I got the new 780i and the new x4 ultra psu, the problem started, I called evga tech support and they decided the board was bad and sent me a second one. ( it was a cross shipment so now I have two 780i boards ) The second board does the same thing. I took the same steps as I stated above. Now, I decided that it must be the power supply, and called ultras tech people and they said that the 12.35 volts was in the good range, and that the PSU could still be defective.(12.6 is over the volt range) ( but the PSU worked in the 750i! @$#@!!) So.......I goes to the store and beg the manager to let me replace the ultra x4, even after the 30 day return policy was up, and he did. JOY!! JOY!! I get home with the new PSU , hook it up and.............................. FUC!!!!!!! Same thing. To me It's all revolving around the 780i and the x4 Ultra. Is it that this X4 ultra will just not work with the evga 780i motherboard? Is it possible that the board needs to be grounded better, say, installed in the case? I'm stuck, Is it possable the cpu can function in one motherboard and not the other? I am at a loss on what to do. It's been a lot of time and money. Anyways I cant bash EVGA because they've helped me as much as they can over the phone, I guess. And when they sent out the first 780i they never sent the north bridge fan, i/o shield or sli connectors, so they sent them over night. I still have to call ultra and try some further trouble shooting steps. I'm just wondering if ANYONE has had this problem or knows of it. Thanks. Some steps I've taken: 850 watt thermaltake works in the 780i with the 6800 vid card. 1200 watt x4 ultra works in the 750i with 6800 0r 280 gtx vid card 780i will not work with x4 ultra regardless of video cards didn't try swapping ram,cpu with different one's. don't have it. changed the cmos battery removed and reinstalled the cpu/ram tried to start the board without ram,vid card removed north bridge heat sink to check for thermal problems Called evga tech support called ultra tech support checked evga website for ram and cpu compatibility, it looks like it's tested and approved.