I have done this scores of time for the last five years. The procedure I have always used consists in first installing airtime-easy-setup through software center, then run the following two commands:
sudo apt-get update
sudo apt-get install airtime
After which, all I had to do was to delete the airtime database and then restore my most recent backup, and my station was running fine.
Today, when reproducing the same procedure on my laptop, I have no difficulty in installing aitrime-easy-setup. But, when I enter "sudo apt-get update", I get the following error message:
I'm also trying to install Airtime. The community radio station I'm involved with has had a new computer donated so want to install Airtime 2.5.1 on Ubuntu 12.04.