Tyan 28XX motherboard freeze during large file transfers

I bought several 2882 motherboards and a 2850 motherboard from Tyan and they've been working just fine for 2.5 years until I decided to copy large (1-4GB) files to any machine via GB ethernet.
They are configured w/Windows Server 2003 (one is running RC2) as web and SQL servers (2000).
During a large file transfer, a machine will completely lock up (a hard lockup - OS, keyboard, mouse, completely frozen).
I've eliminated all running apps as the culprit (except the OS - will try a different one).
I've eliminated the NIC as the culprit (replaced w/Intel Pro Server cards and disabled onboard NIC)
I've eliminated the ethernet switches and cables as culprits.
I've eliminated the SATA controller (SI3114) as a culprit (replaced w/RocketRAID and disabled onboard controller).
I've eliminated the CPUs (they work fine in a GigaByte board).
I've eliminated the Corsair ECC 3200 & 2700 memory (works fine, tests fine in other brand boards).
I've upgraded the BIOSes to no effect.
I can reproduce the problem in all machines during large file transfers.
The only chips common to both boards besides the CPU are the following:
• AMD-8111™ HyperTransport™ I/O Hub
• Winbond™ W83627HF Super I/O ASIC

I played email tag w/Tyan for weeks, but they blame the Operating System (though, my other W2K3 servers pump huge data files every night -30GB+!)

I've permanently abandoned Tyan, but I just wanted to see if others using Tyan 2882 or 2850 motherboards have tried copying huge datafiles via Gigabit Ethernet and seen it lock up. Running backup software sometimes, but not always will lock the machines up as well.

Interesting, did u use a ATI video on a PCI-E bus ?