Abit A8N lan problem (nForce4 chipset)

In BIOS 'enable' all options associated with LAN, like I have an NF4 board I have to enable Nvidia LAN and the ethernet adapter shows up in Device manager. Should be under 'onboard devices' or something similiar.

It's okay, but there is just one option in connection with LAN, I think (or not?). This is "LAN Controller" in BIOS. It's 'Enabled' and I see the "Nvidia Nforce Networking Adapter" in the Device manager. The windows says: "This device is working properly.", but it doesn't work.
This is the reason, why I don't understand my problem.

Yeah, I have just gone through this with an old NF4 board, the Nvidia Nforce Networking Adapter showing in Device amnager, configured correctky, but not being able to establish a connection (Right?). I concluded I ran a Registry cleaner and corrupted the registry. That's what I came up with, the registry was corrupted. I reloaded the OS and it fixed it! I'm using the system now.

Registry? I think, it's not in connection with regisrty, because I tried it 4 different operating system, and the problem is the same. But the registry is clean...
(or we misunderstand each other?)

Yeah, not sure we had the same problem with the 'Nvidia Nforce Networking Controller'. I had to enable this controller in BIOS to get it to show up in Device manager. The Controller was configured correctly. I could not establish a network connection. Finally, I reinstalled WIN XP, enabled the Controller in BIOS and everything works perfect.

Yes, unfortunately my problem is a bit different. But thanks for the help!  

What kind of networking cable do you have plugged in between the router and LAN port on your computer? If it's a crossover cable it might not work. Otherwise you may have either a bad cable, or something messing up inside the port itself on the motherboard.

I use a normal Cat5 cable. It's not a crossover one. It works, because it was used before.
What do you mean by "something messing up inside the port itself on the motherboard"? Thanks...

Like a chunk of dust or dirt coving up one of the connector pins. Or one of the pins on the cable or port being corroded/rusty things like that. How long ago was it used, and try and test it on another computer.

Cable is good, because I have a router and a switch too. If I connect the cable beetween the router and the PC, it doesn't work, but it works beetween the switch and the router.
The lan port of my mobo is "physically" good, because randomly it indicates me about the traffic. But just randomly... :S

I am having the same problem w/ my nforce mobo. It seems to pick up the lan, sometimes, and not others. I've had multiple arguements w/ hp over it, because i feel the nforce mobo's (and i've been told so by many people higher on the tech scale than I) share a serial bus with another component. I believe graphical. Their are times this corrupts data, and i believe makes the port inoperable. Only occassionaly does this happen and reverse, for extended periods of time.
I don't have any advice, only the want to know if you find out anything, and any more about your experience.

easiest solution is to put in a cheap network card for about $10-15.. some times its easier to avoid fixing things and buy another card... you could spend many wasted hours on the fact that nforce 4 doesnt use the force !!!

I am having the exact same problem, Ive installed windows xp pro/ xp 64 same issue , installed a known working 3rd party network adapater and it does the same thing. Wierd thing is upon reinstalling the adapters they assign with a new numerical identifier such as network adapater # and rise as you attempt reinstalls. I know the connection is good because im using it on another machine right now. This happened after I let it sit about a month next to my desk. Im going to try reinstalling windows again with a legacy driver for the motherboard.. one from the disc, without the network cable plugged in , followed be an antivirus install before I plug it up again. This is a 3 week problem love to find a solution.

Current State after above explanation Setup :
Windows 64 Completely Fresh install (only motheboard drivers disc installed for chipset. downloaded video most current.)(Old Drivers originally worked.)
Installed Programs : AVG (disabled for troubleshooting)
Network Cable : New
Connection tested on a known working PC.
Bios Settings checked : Asus A8N-Sli

Network Adapter : Stating Network Cable Unplugged.
Also tried another known good motherboard.

I have this problem only when I install 4GB of RAM. When I run 2x1GB + 2x 1GB no network. When I run 2x 1GB + 2x512MB for 3GB total things are fine. I have this same problem on 2 nforce4 systems with different motherboards. Something about going to 4GB causes major problems with them. I'm running Windows 7 Ultimate RTM on both systems that exhibit this behavior.