After installing AIS, ethernet network adapter shows "cable unplugged"

I just have installed Avast Internet Security on a laptop (Win 7) and after the final restart now the ethernet network adapter shows “cable unplugged”. I can see the light next to the network cable is ON.

This is a second laptop (Win7) where I have exactly the same problem - different laptop modes and different network cards the only thing in common is - the problem appeared after installing AIS.

Any ideas?