logout takes three minutes to get to login screen

[Michael Murray]

13.10
lightdm
I expected to confirm logout and be returned to the login screen within ten seconds or so.
It takes a full 180 seconds to complete logout. Screen icons vanish immediately, the panel/system bar disappears after 60 seconds, and the full login screen with login options and panel appears after three minutes.

Have seen other users of xubuntu and fglrx proprietory drivers ask for help on AskUbuntu, which made me suspect a bug.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: lightdm 1.8.4-0ubuntu1
ProcVersionSignature: Ubuntu 3.11.0-13.20-generic 3.11.6
Uname: Linux 3.11.0-13-generic x86_64
ApportVersion: 2.12.5-0ubuntu2.1
Architecture: amd64
Date: Fri Nov 22 18:24:11 2013
InstallationDate: Installed on 2013-11-20 (2 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
MarkForUpload: True
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)