update-apt-xapian-index crashed with OSError in info(): [Errno 5] Input/output error: '/usr/share/app-install/desktop/'

Binary package hint: apt-xapian-index

running updates via synaptic, got the error message on rebooting to complete updates.

ProblemType: Crash
DistroRelease: Ubuntu 11.04
Package: apt-xapian-index 0.41ubuntu5
ProcVersionSignature: Ubuntu 2.6.38-6.34-generic 2.6.38-rc7
Uname: Linux 2.6.38-6-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
Date: Sun Mar 13 13:13:33 2011
ExecutablePath: /usr/sbin/update-apt-xapian-index
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha amd64 (20110302)
InterpreterPath: /usr/bin/python2.7
ProcCmdline: /usr/bin/python /usr/sbin/update-apt-xapian-index --update -q
ProcEnviron:
 LANGUAGE=en_US:en
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
PythonArgs: ['/usr/sbin/update-apt-xapian-index', '--update', '-q']
SourcePackage: apt-xapian-index
Title: update-apt-xapian-index crashed with OSError in info(): [Errno 5] Input/output error: '/usr/share/app-install/desktop/'
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: