I have a very strange and specific problem that I have spent much time troubleshooting...
I recently decided to bring back an old Lenovo ThinkPad T61 Windows 7 64-bit laptop back to use after 3.5 years of being dead (I replaced the motherboard which failed). It has an Intel 4965AGN wireless-N card.
Unfortunately, I am having intermittent internet drops when it comes to IPv4 websites, with being unable to visit such websites anywhere from 5 to 20 minutes at a time before it (sometimes) restores itself. To clarify, I am still able to visit Google, YouTube, Facebook, and Yahoo this whole time as these are all on IPv6. The entire time with these random drops, the WiFi stays connected and the IPv4 and IPv6 in the network connections all show "Internet" next to the IPv4 and IPv6 Connectivity. I can fix the internet drops by disconnecting and reconnecting to the WiFi network, but it's annoying to keep doing this.
The only indication that there is an IPv4 internet issue is with being unable to access those websites and receiving a "Request Timed Out" when I try to ping a website in Command Prompt. Windows 7 and the WiFi adapter the entire time think they're connected and that there is no problem.
I have tried the following:
1) Flushing the DNS
2) Changing the DNS to Google's DNS (220.127.116.11 and 18.104.22.168)
3) Resetting the TCIP stack
4) Resetting the Winsock
5) Releasing and renewing the IP
6) running virus and malware scan
7) Disabling IPv6.
8) Running SFC /scannow
9) Trying multiple drivers from both Intel and Lenovo
10) Changing between 2.4Ghz and 5Ghz.
Nothing made a difference.
I finally decided to do a clean install of Windows 7, and the problem still occurs. I am still running the laptop barebones with just Spotify and Mozilla Firefox as the only non-Microsoft software, however the internet drop occurred before I installed these two software, so they're certainly not the cause.
It's connected to a new LinkSys EA7300 router, a very fast dual band MIMO router. No problems between the new EA7300 and my Lenovo ThinkPad Windows 10 laptop (which has an Intel Wireless-AC 7260), Android smartphone, iPad (old first generation), and Yamaha MusicCast system, so I do not believe it is a router problem.
What could be the cause of this conflict? What router or wireless card changes can I try to fix this issue?
I am still testing this, but I have found that disabling "802.11n Mode" in the Device Manager properties of the wireless card resolves the problem, however, this is not an ideal solution as it limits the speed to 54mbps (802.11g).
Would appreciate any help on this as I'm out of ideas.