Gigabyte GA-6BXC

I recently had 2 systems running Celeron 300A on Gigabyte GA-6BXC boards with 160MB SDRAM crash for no reason. They don't post at all, and all I get is the red HD indicator light when I power them up. I've tried different processors, new RAM, new HD's, and even a new ROM chip. But nothing has worked. The processor fan gets power, so it wouldn't make sense for it to be the motherboard. The only other equipment that I'm running are a 3COM 3C905B 10/100 NIC card, and ATI Rage II card. The modifications that have been made recently were changing the PS on both of them (as they both fried), the RAM has been upgraded from 32 MB to 160 MB, the OS from 95 to 2K, and the BIOS was upgraded. I've made this upgrade to 10 other systems and none of them have had a problem. Both of these machines have been running fine for the last 2 weeks since they were upgraded. One of them crapped out yesterday, and the other one today. If anyone can make some sense of this, and has some suggestions I would greatly appriciate it. Thanks in advance.

Specs of systems in question:
Celeron 300A
Gigabyte GA-6BXC
160 MB SDRAM
3COM 3C905B 10/100 NIC
ATI Rage II
Antec 250W PS

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T-Bird 1.2 GHz 266 FSB
256 MB PC2100 DDR
EpOX 8K7A+
Elsa Gladiac GeForce2 MX
2 Maxtor 40 GB 7200 ATA/100 HD's
SB Live! Value
3Com 3C905B-TX 10/100
TDK VeloCD 8/4/32