Cannot open local help file

When I click the Help button on a Gnome dialog box, the help browser opens with the following message:
The file ‘/usr/share/gnome/help/user-guide/en_GB/user-guide.xml’ could not be parsed because one or more of its included files is not a well-formed XML document.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: yelp 3.0.0-0ubuntu2
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
Architecture: i386
Date: Wed Sep 7 00:51:31 2011
ExecutablePath: /usr/bin/yelp
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
ProcEnviron:
 LANGUAGE=en_GB:en
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: yelp
UpgradeStatus: No upgrade log present (probably fresh install)