I don't know if this is relevant or not, but here's the log from the first system bootup after swapping MB-CPU-RAM-NIC:
Code:
	Aug 2 17:48:55 nas kernel: rx-checksum: enabled
	Aug 2 17:48:55 nas kernel: tx-checksum: enabled
	Aug 2 17:48:55 nas kernel: scatter-gather: enabled
	Aug 2 17:48:55 nas kernel: irq moderation: disabled
	Aug 2 17:48:55 nas kernel: role: slave
	Aug 2 17:48:55 nas kernel: flowctrl: symmetric
	Aug 2 17:48:55 nas kernel: duplex mode: full
	Aug 2 17:48:55 nas kernel: autonegotiation: yes
	Aug 2 17:48:55 nas kernel: speed: 1000
	Aug 2 17:48:55 nas kernel: eth0: network connection up using port A
	Aug 2 17:48:51 nas kernel: eth0: network connection down
	Aug 2 17:39:41 nas weblogger: Invalid password from 192.168.1.22
	Aug 2 17:39:21 nas kernel: rx-checksum: enabled
	Aug 2 17:39:21 nas kernel: tx-checksum: enabled
	Aug 2 17:39:21 nas kernel: scatter-gather: enabled
	Aug 2 17:39:21 nas kernel: irq moderation: disabled
	Aug 2 17:39:21 nas kernel: role: slave
	Aug 2 17:39:21 nas kernel: flowctrl: symmetric
	Aug 2 17:39:21 nas kernel: duplex mode: full
	Aug 2 17:39:21 nas kernel: autonegotiation: yes
	Aug 2 17:39:21 nas kernel: speed: 1000
	Aug 2 17:39:21 nas kernel: eth0: network connection up using port A
	Aug 2 17:39:18 nas kernel: eth0: network connection down
	Aug 2 17:38:53 nas kernel: rx-checksum: enabled
	Aug 2 17:38:53 nas kernel: tx-checksum: enabled
	Aug 2 17:38:53 nas kernel: scatter-gather: enabled
	Aug 2 17:38:53 nas kernel: irq moderation: disabled
	Aug 2 17:38:53 nas kernel: role: slave
	Aug 2 17:38:53 nas kernel: flowctrl: symmetric
	Aug 2 17:38:53 nas kernel: duplex mode: full
	Aug 2 17:38:53 nas kernel: autonegotiation: yes
	Aug 2 17:38:53 nas kernel: speed: 1000
	Aug 2 17:38:53 nas kernel: eth0: network connection up using port A