Comment 7 for bug 867871

24da873c870d6a3dbfc17390dda52eb8 *ubuntu-11.10-alternate-i386.iso

I hit this problem too. I didn't use unetbootin, dd'd directly to my usb stick.

Installed to encrypted lvm+btrfs. Failed around the install software phase, tasksel died.

Workaround for me was to:

<alt-f2>
chroot /target /bin/bash
mv /etc/apt/apt.sources /etc/apt/apt.source.orig
cp /etc/apt/apt.sources.apt-conf /etc/apt/apt.sources # can't remember the exact filename, something like this
apt-get install xserver-xorg-video-ati

and then retry the failed menu item in the installer.