My Cygwin ssh client stopped working... It would successfully connect to
the remote (Debian) host but then hang without displaying the command
prompt.  See debug output attached, as well as cygcheck output.

I decided to run setup to see if there was a newer version of openssh.
In preparation for that I always terminate all Cygwin processes because
they will interfere with the update.  I killed the ssh-agent process and
on a whim decided to try connecting again.  This time it worked.

This would seem to indicate something in ssh-agent is interfering with
the connection.  There are no credentials loaded into ssh-agent.

-- 
Jim Garrison
jhg@acm.org