PC help PLZ!!!!

[Vileunknown]

I am 100% posotive that it is not the PSU I just got another one and tried it and it still doesnt work. I checked the case to make sure that the power button was connected properly. Everything is connect correctly. I think that the problem may lie in the motherboard. I disconnected everything from the PC, and slowly plugged pieces in piece by piece. I found that the computer will start up fine when I only have the main power connector and one the ATX 12Volt power connectors. As soon as I plug in the other(The one shaped like a square) it stops working. Unfortunately in order to get the bios you need all three power connectors plugged in. Does this sound like a defective motherboard problem to anyone?

Motherboard: http://www.newegg.com/Product/Product.asp?Item=N82E16813130048

I recently purchased multiple computer parts from newegg, and put them together. I was able to turn the computer on, but it got now signal, so I then noticed that a wire came loose. I replugged in the wire and went to turn on, and it started to boot, but then it just turned off. Now it will not start anymore, no matter what I try. I don't beleive it is a power supply issue, because when I hit the power button it tries to start gfor a second, and everythong tries to light up and he fans begin to spin, but then it shuts down again. My system is:

Antec 550watt

MSI Radeon X1800XT

MSI NVIDIA K9N-SLI-Platinum AM2

AMD AM2 4600+

I'm not a total n00b, I have built multiple PC's before

Please respond quickley, Thanks in advance!!

 

[Vileunknown]

Cmon guys...some of u have to know something...