I had a very similar problem yesterday.
Let's walk through a few things to see if we can solve this:
1. Always , no matter how lame it seems, always check the obvious FIRST. The network patch cable you are running from the NIC to the RJ-45 port of the network, is it quality? Did you run connectivity tests on the patch?
2. I know how some laptop NICs have that little pop up RJ-45 connector, if these NICs have that, make sure it isn't damaged - especially that the "pop out part" isn't bent or that the copper isn't damaged.
3. Never rely on PnP - unless you have installed a particular brand and model of something OVER AND OVER again and it ALWAYS works on PnP. Otherwise , go with manual installs. I'd check the manufacturer websiteof the NICs and search for the latest driver and MANUALLY install it.
4. Are you doing loop back tests at all? Ping 127.0.0.1 - assuming, TCP/IP is properly installed, if you get an error-free ping back..the card is technically fine. If you don'tget a ping response at all - something is wrong with the card. If you get a ping back, but its usually slow or you get errors....it could be just from other network traffic or it could me bad signal quality due to the cabling.
5. Double check your network settings. Also start with a "bare" configuration. Meaning only install what service/protocols you minimally need to connect to your network.
6. Ever think about investigating the RJ-45 ports themselves (if you are trying to connect these computers at specific stations for example). Maybe something as simple as a faulty hub port, or someone was in the switch config and was playing with port assignment parameters.
Look me up in the peer directory and I'll help you further if none of this seems to help.
Take care.
