Same problem here. Happened after I moved the HDD to a new box.

dmesg:

[36487.119709] NETDEV WATCHDOG: eth0: transmit timed out
[36487.119717] eth0: transmit timed out, tx_status 00 status 8601.
[36487.119723]   diagnostics: net 0cfa media 8880 dma 0000003a fifo 8000
[36487.119726] eth0: Interrupt posted but not delivered -- IRQ blocked by another device?
[36487.119829]   Flags; bus-master 1, dirty 3775454(14) current 3775454(14)
[36487.119832]   Transmit list 00000000 vs. f7d67ac0.
[36487.119836]   0: @f7d67200  length 8000004e status 0001004e
[36487.119838]   1: @f7d672a0  length 80000042 status 00010042
[36487.119840]   2: @f7d67340  length 80000042 status 00010042
[36487.119843]   3: @f7d673e0  length 80000042 status 00010042
[36487.119845]   4: @f7d67480  length 80000042 status 00010042
[36487.119848]   5: @f7d67520  length 80000042 status 00010042
[36487.119850]   6: @f7d675c0  length 80000036 status 00010036
[36487.119852]   7: @f7d67660  length 8000004e status 0001004e
[36487.119855]   8: @f7d67700  length 8000004e status 0001004e
[36487.119857]   9: @f7d677a0  length 8000004e status 0001004e
[36487.119859]   10: @f7d67840  length 8000004e status 0001004e
[36487.119862]   11: @f7d678e0  length 8000004e status 0001004e
[36487.119864]   12: @f7d67980  length 80000042 status 80010042
[36487.119867]   13: @f7d67a20  length 8000004e status 8001004e
[36487.119869]   14: @f7d67ac0  length 80000042 status 00010042
[36487.119872]   15: @f7d67b60  length 800005e2 status 000105e2
[36487.119876] eth0: Resetting the Tx ring pointer.

uname:
Linux rogue 2.6.20-16-generic #2 SMP Wed May 23 01:46:23 UTC 2007 i686 GNU/Linux

lspci:

00:00.0 Host bridge: nVidia Corporation nForce3 250Gb Host Bridge (rev a1)
00:01.0 ISA bridge: nVidia Corporation nForce3 250Gb LPC Bridge (rev a2)
00:01.1 SMBus: nVidia Corporation nForce 250Gb PCI System Management (rev a1)
00:02.0 USB Controller: nVidia Corporation CK8S USB Controller (rev a1)
00:02.1 USB Controller: nVidia Corporation CK8S USB Controller (rev a1)
00:02.2 USB Controller: nVidia Corporation nForce3 EHCI USB 2.0 Controller (rev a2)
00:08.0 IDE interface: nVidia Corporation CK8S Parallel ATA Controller (v2.5) (rev a2)
00:0a.0 IDE interface: nVidia Corporation CK8S Serial ATA Controller (v2.5) (rev a2)
00:0b.0 PCI bridge: nVidia Corporation nForce3 250Gb AGP Host to PCI Bridge (rev a2)
00:0e.0 PCI bridge: nVidia Corporation nForce3 250Gb PCI-to-PCI Bridge (rev a2)
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
01:00.0 VGA compatible controller: nVidia Corporation NV44A [GeForce 6200] (rev a1)
02:07.0 Multimedia audio controller: Ensoniq ES1371 [AudioPCI-97] (rev 08)
02:08.0 Ethernet controller: 3Com Corporation 3c905C-TX/TX-M [Tornado] (rev 74)
02:09.0 Ethernet controller: 3Com Corporation 3c905C-TX/TX-M [Tornado] (rev 74)
02:0d.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10)


/proc/interrupts :


           CPU0       
  0:    9207088   IO-APIC-edge      timer
  1:          2   IO-APIC-edge      i8042
  6:          5   IO-APIC-edge      floppy
  7:          1   IO-APIC-edge      parport0
  8:          3   IO-APIC-edge      rtc
  9:          0   IO-APIC-fasteoi   acpi
 10:          0   IO-APIC-edge      MPU401 UART
 14:      79160   IO-APIC-edge      ide0
 16:          0   IO-APIC-fasteoi   ohci_hcd:usb1
 17:       4381   IO-APIC-fasteoi   ohci_hcd:usb2
 18:          3   IO-APIC-fasteoi   ehci_hcd:usb3
 19:          0   IO-APIC-fasteoi   libata
 20:    7507139   IO-APIC-fasteoi   eth0
 21:     722950   IO-APIC-fasteoi   eth2
 22:    2249730   IO-APIC-fasteoi   nvidia
 23:      39967   IO-APIC-fasteoi   Ensoniq AudioPCI
NMI:          0 
LOC:    9207215 
ERR:          1
MIS:          6