[SLUG] Tricky ssh question

[jam <jam@xxxxxxxxx>]

Hi

Somewhere on the internet is my father-in-law

Using a fresh install of Gutsy, and having apt-get install openssh-server he tunnels to me

ssh -R 1200:localhost:22 ian@xxxxxxxxx

I then go back the tunnel to his machine

ssh -p 1200 ian@localhost

and get the dreaded
ssh_exchange_identification: Connection closed by remote host

Now the interesting bits:
If he does this with a SuSE10 machine everything works

If I do it on another fresh-gutsy somewhere else on the
internet it works

So it seems specific to ubuntu AND his isp toucansurf.com (uk)

All the googling seems to not apply to this case. Anybody? Help!

Debug -v -v -v shows lots, but until the final coup-de-grac everything 
looks identical on my working eg and his not working eg

ie pages and pages identical, last line on his the exchange issue, on
mine continue with authentication.
 
James