Comment 8 for bug 288479

Confirmed, this seems to affect any installation via the "try Ubuntu" route (rather than "install Ubuntu"). The problem is that ubiquity drops privileges, but fails to regain them correctly before reconfiguring certain packages. The affected files are those which are written by the package reconfiguration process.

Some of them will be automatically cleaned up over time and as updates are released. I've categorized them as follows:

daily:
/var/lib/apt/extended_states
/var/lib/apt/cdroms.list
/var/lib/apt/lists/*

any package update:
/var/cache/debconf/config.dat-old
/var/cache/debconf/config.dat
/var/cache/debconf/templates.dat-old
/var/cache/debconf/passwords.dat
/var/cache/debconf/templates.dat
/var/lib/dpkg/status-old
/var/lib/dpkg/available-old
/var/lib/dpkg/status
/var/lib/dpkg/diversions
/var/lib/dpkg/available
/var/lib/dpkg/triggers/Unincorp
/var/lib/dpkg/diversions-old

kernel update:
/initrd.img
/vmlinuz
/boot/vmlinuz-2.6.27-7-generic
/boot/initrd.img-2.6.27-7-generic
/boot/grub
/boot/grub/xfs_stage1_5
/boot/grub/jfs_stage1_5
/boot/grub/minix_stage1_5
/boot/grub/e2fs_stage1_5
/boot/grub/stage1
/boot/grub/reiserfs_stage1_5
/boot/grub/stage2
/boot/grub/default
/boot/grub/device.map
/boot/grub/fat_stage1_5
/boot/grub/installed-version

locales update:
/var/lib/belocs/hashfile.old
/var/lib/belocs/hashfile

various updates:
/var/lib/gconf/debian.defaults/%gconf-tree.xml
/var/cache/ldconfig/aux-cache
/etc/ld.so.cache

tzdata update:
/etc/localtime

don't care:
/var/log/installer
/var/log/installer/partman
/var/log/installer/initial-status.gz

would have to be fixed manually(?):
/etc/papersize
/etc/popularity-contest.conf
/etc/initramfs-tools/conf.d/resume
/etc/fstab
/etc/hosts
/etc/X11/xorg.conf
/etc/default/console-setup
/etc/default/locale
/etc/apt/apt.conf.d/00trustcdrom
/etc/apt/sources.list
/var/lib/locales/supported.d/local
/media/cdrom0
/media/cdrom1
/media/cdrom
/cdrom