To install bacula on Ubuntu, you need to add the universe repositories to /etc/apt/sources.list. It's just a matter of uncommenting four lines:
deb http://ca.archive.ubuntu.com/ubuntu/ dapper universe 
deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper universe
...
deb http://security.ubuntu.com/ubuntu dapper-security universe
deb-src http://security.ubuntu.com/ubuntu dapper-security universe
Then:
sudo apt-get update
The standard install of bacula uses sqllite, which the bacula guy reports as having problems...