Many users including me [I use kubuntu in pen drive] have faced the problem with it’s default Network Manager! It just doesn’t seem to remember my Network settings which is very annoying indeed! So here is how i sorted it out, see if this works for you as well:
sudo apt-get remove network-manager-kde [or knetwork-manager or network-manager]
Now with your favourite text editor [I’m using kwrite] open up:
sudo kwrite /etc/network/interfaces
iface eth0 inet dhcp [incase of static just put “static” instead of dhcp]
address [your IP address]
netmask [your netmask]
gateway [your gateway address]
^….Not with [ brackets! ]
Now create if you don’t have already a file in /etc/resolv.conf and add your DNS servers:
namserver [your DNS]
For multiple nameservers just keep on adding “nameserver address” in a new line.
Then do sudo /etc/init.d/networking restart
See if this works!