Okay, Windoze can do weird things when you let it install your hardware.
So, uninstall your nic card through the device manager, reboot, when Windoze says it wants to install your nic, click "cancel", then install yourself. Reboot, and see if that fixes the problem.
Also, did you uninstall the drivers for your old vidcard before installing the new one? Another thing, was it an nVidia card? Old drivers can be causing a conflict with your nic.
Always run Driver Cleaner Pro:
http://majorgeeks.com/Driver_Cleaner_Professional_d3214.html in safe mode, after uninstalling drivers, then reboot, and install your new drivers yourself, don't let Windoze install them.
Let us know how that works out for you.