Windows 7 intermittently drops wired Internet/LAN connection

SOLUTION FOUND:

I feel incredibly embarrassed to admit this, but I finally found the solution to my problem and, for me and my problem at least, it was a very easy fix.

In a nutshell, it was a dodgy network cable between my PC and my router. Although brand new, the cable was obviously intermittently defective, and replacing the cable (ironically, with my older, more battered and twisted but perfectly functioning network cable), my LAN has worked perfectly ever since without a single "drop". (And this is over the course of 4-5 weeks of "testing" to ensure that the intermittent problem had really disappeared).

What is interesting, and what completely threw me off the "scent" of looking at the physical hardware was how the problem manifests itself in Windows 7.

Basically, there must have been a slightly loose connection or wire in the LAN cable. When this would "break", Windows would show a broken LAN icon in the task tray area. This would remain broken until I manually went into the LAN Adapter properties, disabled the LAN, then re-enabled it. It was this software-driven temporary "fix" that lead me to believe that the fault itself was entirely software (ie. Operating System) based, rather than physical. Every time the LAN icon would show as "broken", I could "fix" the issue with this disable/re-enable series of steps. Every time!

After exhausting all the software avenues, I started on the hardware. I changed my router for a different one at first and that didn't "solve" the problem. Then I tried the LAN cable. Bingo!

Of course, due to the intermittent nature of the problem, every time I'd try something new, I'd have to "run with it" for a number of weeks to ensure that the problem had gone away (or not, in most cases) since even when the problem was there, I'd been able to go for 5-7 days without a single LAN "break" prior to the issue rearing it's ugly head again. This explains why I'm answering my own question 4 months later! :)

I've now been running with my new (old) LAN cable for 4-5 weeks, and in that time the network connection has not dropped once. I therefore believe I've fixed my problem.

I'm sharing my solution here in the hope that anyone else suffering from the same symptoms can try changing the LAN cable first (despite the symptoms looking very much like a software problem!) :)

I'd also like to thank everyone that responded with various suggestions! Thanks!

Some things to try:

1. In a command prompt (runned as administrator):

   netsh int ip reset intipreset.log
   Reset the TCP/IP stack = reset/rewrite the following TCP/IP-related registry keys:

   * SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\
   * SYSTEM\CurrentControlSet\Services\DHCP\Parameters\
   

   (you may need to re-configure your TCP/IP settings after that)

   netsh winsock reset
   Repair winsock It removes all Winsock LSP (Layered Service Providers) previously installed, including the potential malfunctioned LSP that causes loss of network packets transmission failure. So all previously-installed LSPs (antivirus/firewall) may need to be reinstalled

   netsh interface reset all
   Reset all interfaces: 6to4, HTTPSTunnel, ipv4, ipv6, isatap, portproxy, tcp, teredo
   But I don't know exactly what you risk to do it (not much I think, except reinstalling/reconfiguring network related software & windows parameters...)

2. Uninstall your actual driver and install the one from asus: Realtek RTL8111C LAN Driver V7.3.522.2009 for Windows Win7 32bit/64bit

3. Uninstall the asus driver and install the one from realtek: 7.011

4. Find all .inf files in c:\windows\inf containing references to realtek lan drivers and move them all in another directory, except one. Remove your network card in the device manager and reboot. The one you left should be reinstalled. Test... If the issue is not resolved try another .inf file.

Unbelievably, my drops from my Lenovo ThinkPad Y460 were almost entirely from the laptop going to my wireless box and that was the only computer running Windows 7.

My router is connected to a wireless bridge, which works flawlessly.

I shut down the Windows firewall, installed ZoneAlarm and the problems are gone.

Get rid of the Windows Firewall and use something like the free ZoneAlarm.