When I press "Print Screen" key to make a screenshot, nothing happens

When I press "Print Screen" key to make a screenshot, only see the effect of "take a photo" in the desktop (a flash effect), but nothing happens: the "Save screenshot" window doesn't appear. The screenshot is saved with the name "Screenshot at <time>", but can't select where to save it.

This works if I open "gnome-screenshot" from the launcher.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: gnome-screenshot 3.3.2-0ubuntu2
ProcVersionSignature: Ubuntu 3.2.0-12.21-generic-pae 3.2.2
Uname: Linux 3.2.0-12-generic-pae i686
ApportVersion: 1.91-0ubuntu1
Architecture: i386
CasperVersion: 1.303
Date: Thu Feb 9 19:18:51 2012
LiveMediaBuild: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha i386 (20120201.1)
ProcEnviron:
 PATH=(custom, no user)
 LANG=es_ES.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-screenshot
UpgradeStatus: No upgrade log present (probably fresh install)