Dual network cards on a HP Proliant ML350 G6, not setup in a team. Server 2003 OS.
The primary NIC has a public IP (a Cisco router in transparent bridge mode is in front of it, firewalling all traffic except port 80).
The secondary NIC has a private IP and connected to a private network.
The server runs IIS web server only.
After installing a third NIC (USB Trendnet NIC) a few weeks back (wish I never had) - primary NIC now kind of goes offline after about 24 hours or less.
When I say "kind of" - the NIC is up, appears normal, and I can ping the gateway from the inside. But you cannot access the web server from the outside. Also - we had port 20000 tunneled in for RDP which would also stop working when the NIC seemed to go down. Removed the port forwarding and set the server back to the default 3389 but no change.
Running a repair on the NIC or rebooting fixes it, short term.
Uninstalled the Trendnet drivers software, no change. Updated the drivers from what it was using before to the HP drivers from HP's site, no change.