Had the same problem on ASUS K40IJ and it is with network card Atheros AR8121/AR8113/AR8114.
The problem is the network card. At every boot it changes the MAC address, so the OS identifies it as a new device.
The problem is solved in two ways:
1. To carry in SC on a guarantee.
2. To flash the eeprom on the network card.
My laptop warranty has ended, and you can find the firmware for this card on the Internet failed.