P5n32-e sli plus - strange network issue

I was wondering if anyone else had seen this...

I have a p5n32-e sli plus (the hybrid with the nvidia 680i.) The board has been rock solid running Vista Ultimate x64 since I first purchased it about 18 months ago.

The past 6 to 8 weeks, I've seen the network connection suddenly decide to go to sleep. I have Vista set to never sleep/hibernate and the NIC properties are also set to not allow the OS to turn it off to save power. The network connection will briefly slow to a crawl and then just stop working entirely.

I've tried both the Microsoft driver that came with the OS and also two different 15.x driver releases from nVidia with the same results. I've tried swapping over to the second NIC with the same issue and it doesn't seem to matter whether one is disabled in BIOS or not.

I've Googled multiple instances where people complain about this chipset suddenly 'losing' an entry for the embedded NIC where they have to power down, reboot multiple times, etc, for the entry to come back in the device manager. This isn't something I've seen but the NIC falling asleep at random intervals and for random durations is getting quite irritating.

Here's the kicker... I've tried disabling both embedded NICs and I've tried two different PCI ethernet cards in this motherboard which would exhibit the SAME ISSUE as the embedded NIC (they'd 'fall asleep' as well when installed in this board.) I've done as much isolation as I can... I've swapped out network cables, swapped switches, swapped switch ports, etc. The only constant I've seen is the motherboard itself of something screwy with the embedded NIC or the Vista Ultimate 64 drivers from both Microsoft and nVidia.

Because the board went 18 months without this 'feature' I'm almost to the assumption that something simply died in the PCI bus or something. Power supply, CPU, memory test fine... motherboard posts fine, and other usual tests. I did re-install just last week to try and rule out Vista itself as a probable cause but on a brand new install the problem was still present. I'm hesitant to go buy a replacement board since I don't want to re-install Vista with all my other software again. I also am planning on going to an i7 platform 1Q09 anyway... stats for the system should show up in my signature.