Je sources.list is nogal incompleet, neem deze:
deb http://nl.archive.ubuntu.com/ubuntu dapper main restricted universe multiverse
deb-src http://nl.archive.ubuntu.com/ubuntu dapper main restricted universe multiverse
deb http://nl.archive.ubuntu.com/ubuntu dapper-updates main restricted universe multiverse
deb-src http://nl.archive.ubuntu.com/ubuntu dapper-updates main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu dapper-security main restricted universe multiverse
deb-src http://security.ubuntu.com/ubuntu dapper-security main restricted universe multiverse
deb http://www.ftd4linux.nl/releases/ubuntu dapper ftd
deb-src http://www.ftd4linux.nl/releases/ubuntu dapper ftd