-Internet provided by ATT Uverse via their default gateway/router. (have had 6 months, no problems til now)
-2 PC's running Windows 7 (1 Pro, 1 Home), 1 PC running XP
Approximately 4 days ago, I lost connection with the internet, the network connection was still there, but there was no internet access. Resetting the gateway restored connection for approximately ~10 minutes and then it would drop out again. ATT was called and they hotswapped out a new gateway. The connection worked fine for ~24 hours, and then the same problem started happening, where resetting router would restore internet for brief periods of time.
Then I noticed if I removed the network cable from the PC running Win 7 home, the internet would begin working for the remaining computers. I called ATT and asked for escalated tier service, but they didnt know. So they sent a technician. He came and was baffled as well as to how 1 PC was killing the internet for the rest of the network. He gave me a USB wireless card to try. This seemed to fix the issue, until I woke up this morning with the same problem.
Another strange issue, when I was having these problems, the internet would last longer late at night, it worked for 2-3 hours vs 10 minutes when I would reset late at night. It makes no sense.
There are no setting differences between any computers, and no new devices or were any changes made to any PC in the last 4 days.
I tried different wires, different ports on the gateway, etc. heck even the wireless.
When the internet is working, the speeds are fine.
There is no unusual network activity running it the background, no malicious software was found by malwarebytes , etc.
If you take the other machines off the network and just leave the Windows 7 PC, does it stay working? Perhaps the NIC on the Win7 machine is bad and causing feedback on the network. I have seen similar things happen before.
I don't know if this causes the problem but try it,network cards determine automatically the "speed" of network connection so try disabling network speed auto detection from
network settings-right click then then to the connection of your card-properties-configure and then advanced tab at the left list look for either link-speed or media type click there and on the right of the screen must be a value set to auto change the value to either 10Mbps or 100,keep in mind to check the box full or hald duplex to full.reboot and see what happens