ssh login timeout but scp works

Problem:
ssh login timeout
scp and sftp work

Analysis:

scp and sftp working means port 22 works.

This was due to my router blocking TCP keepalive messages when I connected wirelessly (go figure).

Solution:

ssh my_server -o TCPKeepAlive=no 

From the documentation:

TCPKeepAlive
  Specifies whether the system should send TCP keepalive messages
  to the other side. If they are sent, death of the connection or
  crash of one of the machines will be properly noticed.  However,
  this means that connections will die if the route is down tem-
  porarily, and some people find it annoying.  On the other hand,
  if TCP keepalives are not sent, sessions may hang indefinitely on
  the server, leaving "ghost" users and consuming server resources.

  The default is "yes" (to send TCP keepalive messages), and the
  server will notice if the network goes down or the client host
  crashes.  This avoids infinitely hanging sessions.

  To disable TCP keepalive messages, the value should be set to
  "no".