Problems with my home-built computer and Windows 7

I'm posting this to see if anybody out there has run into similar issues with their home-built computer.  I'm hoping someone has been able to resolve this issue, because I'm having absolutely no luck.

I built a computer a few years back based around an ASUS M2N-E SLI motherboard.  A few months ago, I loaded Windows 7 RC on it, and had very few problems... at least, not the problems I've having now.  Encouraged by what I saw with the RC, I went ahead and pre-ordered a copy of Windows 7 Home Premium for that computer.  Well, in the time between my pre-order and receiving my disks, the network interface stopped working.  I don't believe it to be hardware (though I'm not entirely sure on that), because there hadn't been any storms or anything in my area... no "event" to point to that would give me a reason to think hardware... but of course I can't entirely rule out hardware.  The NIC is on the motherboard, and I'm not having any other issues with the function of the computer.  The NIC also shows up in the Device Manager, so ... well... I don't know what to think there.

I checked ASUS's website, and the M2N-E SLI is not listed as one of their Windows 7 supported motherboards, which is extremely disappointing, to say the least.  This computer isn't very old, and so I was hoping that I wouldn't have to wrestle too much to get it to work.  Does anybody have any advice or recommendations for me?  Any help would be greatly appreciated.