installer hangs forever if Default-Release is set in apt.conf

[Peter Hurley]

When installing over an existing installation (necessary if an update crashes half-way through :( ) and /etc/apt/apt.conf has the Default-Release set (eg, to "natty"), then the installer will quietly hang at "Saving installed packages".

I discovered what the problem was by:
1. booting from the install CD
2. selecting "Try Ubuntu" (rather than "Install Ubuntu")
3. opening a terminal
4. starting the installer with debug logging on; ie., ubiquity -d
5. this popped up a dialog indicating a system problem
6. looked at the intended report which complained that APT:Default-Release = "natty" was not in the repository

I manually fixed it by temporarily mounting the root volume and deleting the ...../etc/apt/apt.conf file.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 3.0.0-14.23-generic 3.0.9
Uname: Linux 3.0.0-14-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Thu Jan 5 10:24:34 2012
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[dino99 (9d9)]

This version has expired for some time