Ubuntu network keeps giving Network Disconnected - You are now offline message

Question

On the face of it, you will find that this is a common question but please read it completely to understand the specific issue that I have.

I am running Ubuntu 12.04.4. I keep getting this network disconnected message but sometimes the network is steady. I have a ppp0 connected to the Internet and eth0 connected to a switch on which I have a Windows machine and a Mac connected. Very simple indeed. I get this message for the eth0 port:

**Wired Network. 
Disconnected - You are now offline**   

Ifconfig for eth0 shows the following:

eth0 Link encap:Ethernet  HWaddr 00:1e:90:a4:ca:67  
     inet addr:192.168.1.50  Bcast:192.168.1.255  Mask:255.255.255.0
     inet6 addr: fe80::21e:90ff:fea4:ca67/64 Scope:Link
     UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
     RX packets:4971 errors:0 dropped:0 overruns:0 frame:0
     TX packets:21127 errors:0 dropped:0 overruns:0 carrier:0
     collisions:0 txqueuelen:1000 
     RX bytes:403400 (403.4 KB)  TX bytes:4351281 (4.3 MB)

I tried changing the switch, the LAN card, the cables too. Then I came across this solution:

 stop network-manager
 sudo rm /var/lib/NetworkManager/NetworkManager.state
 start network-manager

So I decided to go through the GUI for setting the network port parameters but I do not want to do that because I would rather go through command line interface such as ifconfig. Well, through System Settings-> Network ->... giving the IP address and the rest keeps the connection stable.

My question is what is it that the UI is doing that I am missing in ifconfig or any other command that I can use to get around this problem. I want to avoid the use of GUI for network settings at all cost. I find it convenient to deal with the basic linux networking files and commands. From that perspective, what am I missing or doing wrong which pops this error?

Thanks