Whichever most recent version of gnome-screensaver got into Oneiric within the last couple of days constantly tries to dim the display and, in doing so, steals focus away from whatever application the user is utilizing.
This, among other things, resulted in this bug taking 20 minutes to fill, in a situation where 2 minutes would normally suffice, simply because I kept on having to click anywhere in Firefox to prevent gnome-screensvaer from stealing the focus again.
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: gnome-screensaver 3.2.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-12.19-generic 3.0.4
Uname: Linux 3.0.0-12-generic i686
ApportVersion: 1.23-0ubuntu2
Architecture: i386
Date: Sat Oct 1 13:44:31 2011
ProcEnviron:
LANGUAGE=fi:en
PATH=(custom, user)
LANG=fi_FI.UTF-8
SHELL=/bin/bash
SourcePackage: gnome-screensaver
UpgradeStatus: Upgraded to oneiric on 2009-09-14 (747 days ago)
did you set the screen sleep option to "never"?