Strange CPU Failure

So this is my first build ever, just finished it this weekend, and I'm off to a very rough start. Here's my parts list.

Motherboard: Asus Sabertooth Z77
CPU: Ivy Bridge i5-3570K
RAM: Crucial Ballistix 2 x 2GB (1333 MHz)
Boot Drive: Crucial M4 128GB
Storage Drive: Western Digital Black 2TB
PSU: 80+ Gold LEPA 500W
Optical Drive: Not sure... something I pulled out of an old box.

I used the stock fan that came with the CPU, and it worked fine for a day. Then yesterday I got a fan error while booting up. I looked inside the case and indeed the fan seemed to be stuttering. It would try and spin up, slow, stop. Then try and spin up again, repeating the whole process. I did a reboot, and the problem went away. Then today I booted it up again and the problem came back, but it's not going away, no matter how many times I reboot.

I checked that the fan is in the right header, and it is. I looked and I can see 3 headers there. CPU_FAN, CPU_OPT, and CHA_FAN3. Just to be sure it's really the fan I tried to boot up with the thing plugged into one of these other headers. Nothing changed with CPU_OPT, but when I tried the third one the fan started spinning normally. The computer won't accept it though, it still says there is a fan error and goes right into UEFI.

Another thing that puzzles me is that I'm using an Asus board, which comes with Q-LED indicators (those little lights all over the mobo which light up during the boot up). They are supposed to help you solve a boot up problem by staying red at whatever place the problem occurs. Except that when I run into the fan problem, the light stays on at the boot drive... But in UEFI it says my M4 is fine.

Please, any help would be really appreciated. The Sabertooth has a 5 year warranty, but I don't even know if it's to blame. I've ordered an aftermarket CPU fan (a Noctua of some sort), but it will be a few days before it gets here. In the meantime, I'd like to know what my options are. Should I ask NCIX (the supplier I used) to take it all back? It's been under a week so it might work, but I guess I would have to repackage them and pay for the shipping and handling...

I was hoping to get this up and running in time for Diablo III... I doubt I'll make it. But really at this point I just want a working computer.