Screensaver won't exit

[Daedalus Prime]

Binary package hint: acpi

I came back to my computer while the screensaver was running, moved the mouse, and was prompted for my password. Then after entering my password, the screensaver came back on and neither mouse movement nor keystrokes would stop it. I was able to CTL-ALT-F2 to bring up a console. I ran dmesg and noticed the following near the end:

[ 39.684336] Console: switching to colour frame buffer device 128x48
[ 39.684363] fb0: inteldrmfb frame buffer device
[ 39.684365] drm: registered panic notifier
[ 39.695973] acpi device:30: registered as cooling_device2
[ 39.696437] input: Video Bus as /devices/LNXSYSTM:00/device:00/PNP0A03:00/LNXVIDEO:00/input/input12
[ 39.696545] ACPI: Video Device [VID] (multi-head: yes rom: no post: no)
[ 39.696570] [Firmware Bug]: Duplicate ACPI video bus devices for the same VGA controller, please try module parameter "video.allow_duplicates=1"if the current driver doesn't work.

Could that last line be a clue? How do I fix it?

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: acpi (not installed)
ProcVersionSignature: Ubuntu 2.6.38-9.43-generic 2.6.38.4
Uname: Linux 2.6.38-9-generic i686
NonfreeKernelModules: wl
Architecture: i386
Date: Mon May 23 22:23:27 2011
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
ProcEnviron:
 LANGUAGE=en_US:en
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: acpi
UpgradeStatus: Upgraded to natty on 2011-04-29 (24 days ago)