When I start up my computer without having the modem connected, I won't have any internet connection.
However, when there is a connection while I start up the machine I will have internet.
So each time I forget about connecting the computer to the modem before I startup my computer, I have to connect the computer to the modem and restart again.
It does not help to try dhclient when my computer has no internet connection.
I use kubuntu 8.04.