Custom Computer Build Keeps Rebooting- Please help!

Component Specs:
Motherboard- Asus P8Z77-V
CPU-Intel Core i7-3770K
PSU-Corsair CX750W
GPU- Geforce GTX 680
Memory- Corsair Vengeance 16GB (2x8GB)
1600 D3
Windows 8 64-bit

So I've just built my first custom computer. When I tried to start originally the PSU fan starts and the CPU LED blinked for a moment and it all shuts down and restarts. This continues until I cut the power. I researched this and it sounded like the motherboard was shorting out in the case. I took it out of the case tried again and it instantly fixed the problem.

Now when I start the computer it starts up normally and when I leave it alone with nothing running it's fine. But it seems like when I try to download or run something and more power is required it will reboot without any warning. I researched this found several different possibilities. The first one I thought I'd try to fix is the possibility of bad drivers so I went to reinstall Windows 8 and it completely shut down mid process and didn't restart.

Now it's back to the CPU led and PSU fan issue. I've already sent in the motherboard 3 times for faulty CPU and RAM sockets. It's already been 2 months since I bought the parts so I'd really like to avoid sending more stuff in for replacements. Could these two issues be related. Any thoughts on what I can do to fix this?

Thanks in advance!