Most recent kernel where this bug did *NOT* occur: this happens in every kernel
except 2.6.21 (not tested yet)
Distribution: Fedora Core 6
Hardware Environment: 

2 x Intel(R) Xeon(TM) CPU 3.00GHz HT (cpu family : 15, model : 4, stepping : 3)
2 x 1GB ECC DDR RAM
Intel Xeon Motherboard

00:00.0 Host bridge: Intel Corporation E7520 Memory Controller Hub (rev 0c)
00:00.1 Class ff00: Intel Corporation E7525/E7520 Error Reporting Registers (rev 0c)
00:01.0 System peripheral: Intel Corporation E7520 DMA Controller (rev 0c)
00:02.0 PCI bridge: Intel Corporation E7525/E7520/E7320 PCI Express Port A (rev 0c)
00:04.0 PCI bridge: Intel Corporation E7525/E7520 PCI Express Port B (rev 0c)
00:05.0 PCI bridge: Intel Corporation E7520 PCI Express Port B1 (rev 0c)
00:06.0 PCI bridge: Intel Corporation E7520 PCI Express Port C (rev 0c)
00:1d.0 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI
Controller #1 (rev 02)
00:1d.1 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI
Controller #2 (rev 02)
00:1d.2 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI
Controller #3 (rev 02)
00:1d.7 USB Controller: Intel Corporation 82801EB/ER (ICH5/ICH5R) USB2 EHCI
Controller (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev c2)
00:1f.0 ISA bridge: Intel Corporation 82801EB/ER (ICH5/ICH5R) LPC Interface
Bridge (rev 02)
00:1f.1 IDE interface: Intel Corporation 82801EB/ER (ICH5/ICH5R) IDE Controller
(rev 02)
00:1f.2 IDE interface: Intel Corporation 82801EB (ICH5) SATA Controller (rev 02)
00:1f.3 SMBus: Intel Corporation 82801EB/ER (ICH5/ICH5R) SMBus Controller (rev 02)
01:00.0 PCI bridge: Intel Corporation 6700PXH PCI Express-to-PCI Bridge A (rev 09)
01:00.1 PIC: Intel Corporation 6700/6702PXH I/OxAPIC Interrupt Controller A (rev 09)
01:00.2 PCI bridge: Intel Corporation 6700PXH PCI Express-to-PCI Bridge B (rev 09)
01:00.3 PIC: Intel Corporation 6700PXH I/OxAPIC Interrupt Controller B (rev 09)
02:03.0 Communication controller: Digium, Inc. Wildcard TE210P (rev 02)
05:00.0 Ethernet controller: Marvell Technology Group Ltd. 88E8050 PCI-E ASF
Gigabit Ethernet Controller (rev 18)
07:04.0 Ethernet controller: Intel Corporation 82541GI/PI Gigabit Ethernet
Controller (rev 05)
07:0c.0 VGA compatible controller: ATI Technologies Inc Rage XL (rev 27)

Software Environment: Kernel 2.6.20.7
Problem Description:

Sometimes the network behind Marvell Technology (sky2) stops working. A LED
indicates that it's up and receiving packets but no packet can actually pass
through. arping the nearest router gives no response.  Kernel spouts no messages
in such cases. It's strange but ethtool eth1 also says that the network is up
and running at its full speed. rmmoding and modprobe'ing sky2 module solves this
problem.

Steps to reproduce: -