If you have edited the config files, depmod'd and recreated the initramfs after copying the driver in, and the initramfs in default is definitely updated (check the time/date stamp) then it sounds like the driver isn't working for that NIC.
Perhaps do a modinfo e1000 on the machine when booted as a core and note the details, like:
linuxmce@dcerouter:/lib/modules/2.6.22-14-generic$ modinfo r8168
filename: /lib/modules/2.6.22-14-generic/kernel/drivers/net/r8168.ko
version: 8.008.00-NAPIlicense: GPL
description: RealTek RTL-8168 Gigabit Ethernet driver
author: Realtek and the Linux r8168 crew <
netdev@vger.kernel.org>
srcversion: 2E2189C8B2FEE22CF89C4B1alias: pci:v000010ECd00008168sv*sd*bc*sc*i*depends:
vermagic: 2.6.22-14-generic SMP mod_unload 586
parm: speed:force phy operation. Deprecated by ethtool (
. (array of int)
parm: duplex:force phy operation. Deprecated by ethtool (
. (array of int)
parm: autoneg:force phy operation. Deprecated by ethtool (
. (array of int)
parm: rx_copybreak:Copy breakpoint for copy-only-tiny-frames (int)
parm: use_dac:Enable PCI DAC. Unsafe on 32 bit PCI slot. (int)
parm: debug:Debug verbosity level (0=none, ..., 16=all) (int)