Elaborating on what lflashl stated... Rev 2 of this board uses an Atheros ar8131 chipset that is unsupported by OS X as far as I can tell. The Rev 1 board used a Realtek Chipset that was supported out of the box. I'm sure that's one of the reasons why this board got so much acclaim for the being perfect for hackintosh. My Rev 2 based hack runs perfectly with the addition of the Apple USB LAN adapter. If you want to spend less money, there are other 3rd party USB to LAN adapters that will work. Just make sure they advertise to work with Mac. Otherwise you may read a year old review of a model number that worked out of the box but no longer does because the manufacturer switched chipsets without changing the model number.

Here are a few USB ideas:
http://eshop.macsales.com/item/Macally/AIR2NET/
http://store.apple.com/us/product/MB442Z/A
http://www.newegg.com/Product/Produc...-019-_-Product

Here is a PCI idea:
http://www.newegg.com/Product/Produc...-002-_-Product

I must say, that at the end of the day, compared to what you might spend elsewhere and the time you have invested in working out Kexts or EFI strings and all that stuff, the Apple USB LAN adapter is the way to go.