Corsair tx650w not working?

A while back I installed a corsair tx650w power supply. The computer would boot, but immediately after reaching the desktop, it would turn off. However, the computer stayed on if I left it in the BIOS screen. I put my old power supply back in and there were no problems, so I figured it was just a defective power supply. I RMAed the power supply and got a new one. After I installed this one, I still have the same problem. Since I don't think they sent me two faulty power supplies, it probably is something I'm doing wrong, but I have absolutely no idea what it is. It's very possible that I made a mistake since this is the first time that I've tried replacing a PSU. All I did was put the cables of the new PSU where the old PSU cables used to go. The computer I have is just a stock ASUS Essentio CM5570-AP003.