Cannot map shortcut keys to "To Beginning of Next/Previous Page"

I tried following the formula over at http://www.oooforum.org/forum/viewtopic.phtml?p=436015&sid=fb8c7bee852bc1f90abf38336ce98290#436015:

"Go to Tools->Customize->Keyboard
In the first list, find Page Up and Page Down, or Alt + Page Up and Alt + Page Down.
In the lists, choose Navigation and find To Beginning of Next Page and To Beginning of Previous Page.
You can assign them by selecting a key and a function, then click the 'Modify' button.
Under Linux / X11, the Page Up and Page Down keys are called Prior and Next."

...by assigning those functions to various key combinations, and none of them worked. There was no effect whatsoever, even though keys would map to other functions. It seems as though these two particular functions aren't firing. They must be implemented, as the Next Page and Previous Page buttons are working from the Navigator window.

These two functions should be mappable to key combinations for accessibility purposes.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: libreoffice-core 1:3.3.3-1ubuntu2
ProcVersionSignature: Ubuntu 2.6.38-11.50-generic 2.6.38.8
Uname: Linux 2.6.38-11-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
Date: Mon Sep 26 13:22:30 2011
ExecutablePath: /usr/lib/libreoffice/program/soffice.bin
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100427.1)
ProcEnviron:
 LANGUAGE=en_CA:en
 PATH=(custom, user)
 LANG=en_CA.UTF-8
 SHELL=/bin/zsh
SourcePackage: libreoffice
UpgradeStatus: Upgraded to natty on 2011-04-30 (148 days ago)