pcmanfm Gtk-Message: Failed to load module "canberra-gtk-module"

when i try to copy a file on desktop or on a usb all icons hidden;
to restart i print :

pcmanfm --desktop
and set a wallpaper

all return at normal but terminal say : Gtk-Message: Failed to load module "canberra-gtk-module"

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: pcmanfm 0.9.9-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic i686
ApportVersion: 1.23-0ubuntu3
Architecture: i386
Date: Thu Oct 13 17:32:59 2011
InstallationMedia: Lubuntu 11.04 "Natty Narwhal" - i386 (20101203)
Pref_Config_Home_lubuntu:

ProcEnviron:
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SourcePackage: pcmanfm
UpgradeStatus: Upgraded to oneiric on 2011-10-10 (2 days ago)