Problem with Net::SFTP

I apologize if this is not the right place to post a message about a gem
like Net::SFTP - if there is a more appropriate forum please let me
know.

When I try to connect to one SFTP server, everything works great. This
is the code:

require "net/sftp"

class TestSftp
        Net::SFTP.start("<hostname>", "<username>",
                   :password => "<password>")
                   do |sftp|
                   sftp.download!("<remotefile>",
                                  "<localfile>")
        end
end

However when trying to connect to a particular SFTP server, I receive
the following error message:

/var/lib/gems/1.8/gems/net-sftp-2.0.2/lib/net/sftp/operations/download.rb:307:in
`on_open': open <remotefile>: failure (4) (RuntimeError)
        from /usr/lib/ruby/1.8/rubygems/custom_require.rb:27:in
`to_proc'
        from
/var/lib/gems/1.8/gems/net-sftp-2.0.2/lib/net/sftp/request.rb:87:in
`call'
        from
/var/lib/gems/1.8/gems/net-sftp-2.0.2/lib/net/sftp/request.rb:87:in
`respond_to'
        from
/var/lib/gems/1.8/gems/net-sftp-2.0.2/lib/net/sftp/session.rb:947:in
`dispatch_request'
        from
/var/lib/gems/1.8/gems/net-sftp-2.0.2/lib/net/sftp/session.rb:910:in
`when_channel_polled'
        from /usr/lib/ruby/1.8/rubygems/custom_require.rb:27:in
`to_proc'
        from
/var/lib/gems/1.8/gems/net-ssh-2.0.11/lib/net/ssh/connection/channel.rb:311:in
`call'
        from
/var/lib/gems/1.8/gems/net-ssh-2.0.11/lib/net/ssh/connection/channel.rb:311:in
`process'
         ... 26 levels...
        from
/var/lib/gems/1.8/gems/net-sftp-2.0.2/lib/net/sftp/session.rb:801:in
`loop'
        from
/var/lib/gems/1.8/gems/net-sftp-2.0.2/lib/net/sftp/session.rb:786:in
`connect!'
        from /var/lib/gems/1.8/gems/net-sftp-2.0.2/lib/net/sftp.rb:32:in
`start'
        from testSftp.rb:12

Line 307 in download.rb looks like this:

raise "open #{entry.remote}: #{response}" unless response.ok?

However, I really don't know what's going on. One thing to note is that
I can sftp fine from the command line to this particular server - I'm
pretty sure it's not an issue with my login credentials being correct.
I'm wondering if a different protocol is being used and Net::SFTP is
having problems with that. Does anyone have any experience with this?
Thanks.

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I did not mean to post this multiple times - I thought I was seeing a
"Preview" screen and backed up to make minor edits and unwittingly
re-submitted.

I am very sorry for the extra posts/noise.

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