gnome-screenshot truncates dialog windows

Due to visualize bug 896430, it was found under different conditions dialog windows are truncated by gnome-screenshot. Happens with Oneiric and Precise.

## Example truncated-1
Open gcalctool, enable advanced mode.
It starts with 'Degrees' on left drop-down button.
We want to make a screenshot incl. context menu: Temperature -> Celsius
## the dialog opens downwards.

Open gnome-screenshot via GUI or cli:
gnome-screenshot -w --delay=10

Return to gcalctool, select from drop-down list: Temperature -> Celsius
Result of screenshot: Celsius isn't displayed, the dialog window is truncated. (screenshot truncated-1)

## Example truncated-2
Open gcalctool, enable advanced mode.
Instead of 'Degrees' select 'Currency' -> US-Dollar from drop-down list.
We want to make a screenshot incl. context menu: Temperature -> Celsius
## the dialog opens upwards.

Open gnome-screenshot via GUI or cli:
gnome-screenshot -w --delay=10

Return to gcalctool, select from list: Temperature -> Celsius
Result of screenshot: Celsius is displayed, the rest of dialog window is truncated. (screenshot truncated-2)

Expected:
Don't truncate screenshots under different conditions.

## Terminal output:
~$ gnome-screenshot -w --delay=10
** (gnome-screenshot:6996): DEBUG: The GetProfileForWindow request failed: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.ColorManager was not provided by any .service files

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: gnome-screenshot 3.2.1-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-14.23-generic 3.0.9
Uname: Linux 3.0.0-14-generic x86_64
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Wed Jan 4 17:01:37 2012
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
ProcEnviron:
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-utils
UpgradeStatus: Upgraded to oneiric on 2011-10-28 (68 days ago)