Unable to update via Ubuntu Stable PPA

Thank you for all the hard work! I can't wait to try out 1.3, since I stick to the stable releases!

However, I was unable to update to MuseScore 1.3 using the stable PPA. I am accustomed to installing the version available in the Ubuntu Software Center, but now attempted to add the PPA and install 1.3 - this did not work.

I received the following error message after adding the PPA and then running 'sudo apt-get update':

W: Failed to fetch http://ppa.launchpad.net/mscore-ubuntu/mscore-stable/ubuntu/dists/quantal/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/mscore-ubuntu/mscore-stable/ubuntu/dists/quantal/main/binary-i386/Packages 404 Not Found

I hope this is a small problem that can be rectified easily...

Thanks!
Etienne