Post date: 27-Jan-2009 14:00:12
When I tried to clean up my computer, somehow I erased a needed library for running K3B, and also got an error
W: GPG error: http://ppa.launchpad.net hardy Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7781BA0134BEEE14
W: You may want to run apt-get update to correct these problems
SOLUTION
In order to intall the missing package, just reinstall the program
sudo apt-get update
sudo apt-get install k3b
This should fix the first problem. The second one is a little more tricky, but thanks to blackgr (user of ubuntuforums), we have a little script (below), which makes our lives easier. Download, unzip and run it in the konsole
cd Desktop
unzip launchpad-update.zip
sudo ./launchpad-update
sudo apt-get update
The last line is just to check the problem was solved.
Enjoy!