recurring "link down" errors

[Ayman Altounji]

Hi,
Some of our servers are experiencing irregular "link down" situations where the NIC will drop the link. The NIC is the \Device\CpqNF31 model in full duplex 100MBit mode. The Switches are the Cisco Catalyst 5000 series.
Tracing from the switch, the link seems to remain up but the machine does not reply to any ICMP. The LEDs still indicate network activity. There is no connection from NT to the switch. A card reset does not work. Current workaround is to down the server completely and boot up again (no restart!!).
We are experiencing this on a number of similarly configured servers on different switches. The NICs have been exchanged as well and have been placed in different slots. I suspect a driver issue.
My next step is to add a second CpqNF31 NIC on the same driver. I believe it will behave the same way, so this should be proof of driver failure.
Does this sound familiar to anyone?
Thx, Sjef