bzr crashed with NoSuchRevision in _iter_inventories()

[yoosofan]

bzr crashed when it ran the following command in my project
bzr update
Thanks

ProblemType: Crash
DistroRelease: Ubuntu 11.04
Package: bzr 2.3.1-1ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic x86_64
Architecture: amd64
BzrDebugFlags: set()
BzrPlugins:
 bash_completion /usr/lib/python2.7/dist-packages/bzrlib/plugins/bash_completion [2.3.1]
   launchpad /usr/lib/python2.7/dist-packages/bzrlib/plugins/launchpad [2.3.1]
   netrc_credential_store /usr/lib/python2.7/dist-packages/bzrlib/plugins/netrc_credential_store [2.3.1]
   news_merge /usr/lib/python2.7/dist-packages/bzrlib/plugins/news_merge [2.3.1]
BzrVersion: 2.3.1
CommandLine: ['/usr/bin/bzr', 'check']
CrashDb: bzr
Date: Fri Jul 29 00:27:09 2011
ExecutablePath: /usr/bin/bzr
FileSystemEncoding: UTF-8
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
InterpreterPath: /usr/bin/python2.7
Locale: en_US.UTF-8
PackageArchitecture: all
Platform: Linux-2.6.38-10-generic-x86_64-with-Ubuntu-11.04-natty
ProcCmdline: /usr/bin/python /usr/bin/bzr check
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_US.UTF-8
 LANGUAGE=en_US:en
PythonVersion: 2.7.1
SourcePackage: bzr
Title: bzr crashed with NoSuchRevision in _iter_inventories(): CHKInventoryRepository('file:///home/username/Documents/mydoc/hostname/src/subject/research/innovation/database/webrel/.bzr/repository/') has no revision ('<email address hidden>',)
UpgradeStatus: No upgrade log present (probably fresh install)
UserEncoding: UTF-8
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare