Can't lock screen

Similar to bug #10228, I'm currently unable to lock the screen with xscreensaver. Ctrl-Alt-L does nothing, and `xscreensaver-command -lock` reports "xscreensaver-command: already locked." <http://askubuntu.com/questions/120691/xscreensaver-already-locked>.

I've tried the following to get it back up:
$ killall xscreensaver # Returned with exit code 0
$ xscreensaver-command -lock
xscreensaver-command: no screensaver is running on display :0
$ xscreensaver-command -restart
xscreensaver-command: no screensaver is running on display :0
$ xscreensaver
xscreensaver: 14:22:19: "gnome-screensaver" is already running on display :0 (window 0x3a00001)
$ xscreensaver-command -lock
xscreensaver-command: no screensaver is running on display :0

Looks like there might be some conflict between gnome-screensaver and xscreensaver. I've no idea why gnome-screensaver is running - I'm running LXDE and xscreensaver by default.

Workaround: gnome-screensaver-command --exit && xscreensaver &

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: xscreensaver 5.14-1ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-17.30-generic 3.0.22
Uname: Linux 3.0.0-17-generic x86_64
NonfreeKernelModules: wl nvidia
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Tue Apr 10 14:17:53 2012
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64+mac (20101008)
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
 LC_PAPER=en_GB.UTF-8
SourcePackage: xscreensaver
UpgradeStatus: Upgraded to oneiric on 2012-02-24 (45 days ago)