Wired network connection keeps failing.

[Shadow Wizard]

Ok, here is the thing. To start off with, I own the network, and every system connected to it. I run and admin it, so the chances that anyone else has changed anything is essentially zero.
This computer has a wired network connection (The issue) and a wireless one. They are connected to two separate networks. A few days ago the wired card stopped getting an IP address from my router, always ended up with a 169 address. Eventually I just disabled it, and installed a PCI network card.
Now what happens is that all works fine for a while, then stops. Suddenly I am "Not connected to network" despite the fact my ip address hasn't changed. I run the network troubleshooter, it tells me the "Gateway is unreachable" Resets the network card, and all is good. Then after a while the network fails again. Lil help figure this out please. I did already scan with malwarebytes, and everything is fine as fat as its concerned.

 

[Emerald]

make sure that one of the network card does NOT have a gateway assigned to it

 

[Shadow Wizard]

make sure that one of the network card does NOT have a gateway assigned to it

This is already the case. The wireless card's gateway is blank, but its IP and Subnet are set. The wired card receives its IP Via DHCP.

 

[Emerald]

did you check the network cable?

 

[Shadow Wizard]

The network cable was tested with a network cable tester, and also replaced with a known working cable for a short period of time (When I was having issues with the integrated card and not being able to get an IP) The cable made no difference.