try modprobe e1000 and see if it comes back? (there's also the e1000e driver as well I think that is for the latest cards mostly PCIe)
Intel(R) PRO/1000 Network Driver - version 7.3.20-k2-NAPI Copyright (c) 1999-2006 Intel Corporation.
Check lspci to verify it's still there?
# lspci 00:06.0 PCI bridge: Advanced Micro Devices [AMD] AMD-8111 PCI (rev 07) 00:07.0 ISA bridge: Advanced Micro Devices [AMD] AMD-8111 LPC (rev 05) 00:07.1 IDE interface: Advanced Micro Devices [AMD] AMD-8111 IDE (rev 03) 00:07.3 Bridge: Advanced Micro Devices [AMD] AMD-8111 ACPI (rev 05) 00:0a.0 PCI bridge: Advanced Micro Devices [AMD] AMD-8131 PCI-X Bridge (rev 12) 00:0a.1 PIC: Advanced Micro Devices [AMD] AMD-8131 PCI-X IOAPIC (rev 01) 00:0b.0 PCI bridge: Advanced Micro Devices [AMD] AMD-8131 PCI-X Bridge (rev 12) 00:0b.1 PIC: Advanced Micro Devices [AMD] AMD-8131 PCI-X IOAPIC (rev 01) 00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration 00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map 00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller 00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control 00:19.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration 00:19.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map 00:19.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller 00:19.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control 01:00.0 USB Controller: Advanced Micro Devices [AMD] AMD-8111 USB (rev 0b) 01:00.1 USB Controller: Advanced Micro Devices [AMD] AMD-8111 USB (rev 0b) 01:05.0 VGA compatible controller: Trident Microsystems Blade 3D PCI/AGP (rev 3a) 02:02.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5704 Gigabit Ethernet (rev 03) 02:02.1 Ethernet controller: Broadcom Corporation NetXtreme BCM5704 Gigabit Ethernet (rev 03) 02:04.0 SCSI storage controller: LSI Logic / Symbios Logic 53c1030 PCI-X Fusion-MPT Dual Ultra320 SCSI (rev 08)
so the OS cant see the card at all