Comment 1 for bug 820805

This looks similar to a problem a user on IRC ran into recently:
<http://irclogs.ubuntu.com/2011/07/16/%23bzr.html#t13:52>

In that case, I believe it was caused by running the Pageant exe straight from the downloads folder rather than installing it, which on Windows 7 trips some access protections designed to isolate files that come from the internet.