remote connection fails with non-usable error

[reader]

On a recently setup gentoo linux system I've installed cvs and
attempting to co sources from another gentoo box running cvs across a
home lan.

The connection fails immediately once the password is passed through.

  On the remote:
  # echo $CVSROOT
  address@hidden:/usr/local/cvsroot

  # echo $CVS_RSH 
  ssh

So the connection attempt looks like:
  # cvs co base/mob2vm25
  Password:
  Unknown command: `server'
   [...] snip usage
  cvs [checkout aborted]: end of file from server \ 
  (consult above messages if any)

Its been a long time since I've used cvs remotely and my old annotated
commands fail here wrapped for mail).

  This one fails the same way with same error
  cvs -d :ext:address@hidden:/usr/local/cvsroot \
              co base/mob2vm25

I don't recall having to do anything special on repo host for this to
work.  But it looks like the repo machine is rejecting the attempt.
Or misreading the attempt.

The password authentication appears to work

A search of the entire info manual of cvs gives one hit on `verbose'
and it isn't related to a connection attempt.  So apparently it isn't
intended that cvs can be made to give something usefull in the way of
error message.

I see dozens of hits on google searching on the error output.
It appears all to be related to windows machines problems.  But
scanning through some of it anyway hasn't been helpful.