Reasons why erl -remsh might not work?

[Rob Charlton]

I am trying to connect a remote shell to a running erlang node on a
remote customer's site. I am ssh'd into the machine on which the node is
running. It is running Red Hat 4, erlang R12B

If I start (what I think is the same) node on my own machine, then do:
erl -sname test -remsh mynode@REDACTED
then the shell works.

If I ssh to the remote machine and type:
erl -sname test -remsh theirnode@REDACTED -cookie theircookie
then I get:
*** ERROR: Shell process terminated! ...

If I just start a local shell and try:
net_adm:ping(theirnode@REDACTED)
then I get:
pang

If I type:
nodes().
then I get:
[]

At the linux console if I type:
epmd -names
then theirnode is listed.

I can use to_erl to connect to the running node and get a console
session, but there is too much logging output to do anything useful,
hence my attempt to get a remote shell.

I've run out of ideas for what to check next! Does anyone have any
suggestions?

Thanks

Rob