Hi,
The actual proxytunnel (v1.9.0) command which ultimately should just open a two-way pipe between client and remote ssh server is:
proxytunnel -q -e -P <localproxyuser>:<localproxypass> -p <localproxyhost>:<localproxyport> -R <remoteproxyuser>:<remoteproxypass> -r <remoteproxyhost>:<remoteproxyport> -d <targetsshserver>:<targetsshport>
where:
-p, Local proxy host:port combination
-r, Remote proxy host:port combination (using 2 proxies)
-d, Destination host:port combination
-e, SSL encrypt data between local proxy and destination
-P, Proxy auth credentials user:pass combination
-R, Remote proxy auth credentials user:pass combination
-q, Suppress messages
So it connects to local (my work) HTTP proxy, then connects to a remote (my home) HTTP proxy, then ultimately to the remote SSH server. I know that the proxy-chaining proxytunnel does works as this is the same command as I issue in PuTTY and it connects as expected.
For testing, you might be able to just see if the local proxy works by using a netcat command or something as it looks like a problem in passing data through the local command pipe rather than the proxy command or its invocation.