It looks like quagga is designed to not stop the service automatically if it is running. Please try stopping the service manually ('service stop quagga' or '/etc/init.d/quagga stop') and then continue the upgrade.
** Changed in: quagga (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/689472 Title: package quagga 0.99.15-1ubuntu0.1 failed to install/upgrade: subprocess new pre-removal script returned error exit status 1 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs