bzr rebase crashed with "exceptions.AssertionError: Rev changed"

While working on a code reorganization project involving a number of directory moves and file edits, additions and deletions, I did a bzr rebase to try and change the way in which the work was being organized slightly. The rebase command died as follows:

Hal$ bzr rebase ../reorg-anj/
bzr: ERROR: exceptions.AssertionError: Rev changed

*** Bazaar has encountered an internal error. This probably indicates a
    bug in Bazaar. You can help us fix it by filing a bug report at
        https://bugs.launchpad.net/bzr/+filebug
    attaching the crash file
        /home/anj/.cache/crash/bzr-20110225070426-912.crash
    and including a description of the problem.

    The crash file is plain text and you can inspect or edit it to remove
    private information.

The crash file is attached.