update manager "an unhandleable error occured"

[Grayson Kempster]

"There seems to be a programming error in aptdaemon"
Traceback (most recent call last):
  File "/usr/lib/python2.6/dist-packages/aptdaemon/worker.py", line 179, in _process_transaction
    self.commit_packages(*self.trans.packages)
  File "/usr/lib/python2.6/dist-packages/aptdaemon/worker.py", line 227, in commit_packages
    self._commit_changes()
  File "/usr/lib/python2.6/dist-packages/aptdaemon/worker.py", line 738, in _commit_changes
    if self.trans.cancelled:
  File "/usr/lib/python2.6/dist-packages/apt/deprecation.py", line 98, in deprecated_function
    return func(*args, **kwds)
  File "/usr/lib/python2.6/dist-packages/apt/cache.py", line 427, in commit
    res = self.install_archives(pm, install_progress)
  File "/usr/lib/python2.6/dist-packages/apt/deprecation.py", line 98, in deprecated_function
    return func(*args, **kwds)
  File "/usr/lib/python2.6/dist-packages/apt/cache.py", line 394, in install_archives
    install_progress.finish_update()
  File "/usr/lib/python2.6/dist-packages/aptdaemon/progress.py", line 264, in finish_update
    lock.status_lock.acquire()
  File "/usr/lib/python2.6/dist-packages/aptdaemon/lock.py", line 67, in acquire
    raise LockFailedError(self.path, process)
LockFailedError