I have a Lynksis Wireless-G Cable Gateway (WCG200) that I use to
connect remotely (via ssh) to my work linux computer. With my previous
modem I could leave the connection open indefinitely. But with this
modem, as long as I use the remote system everything is fine, but if I
stop typing, the connection hangs after 5-10 minutes of inaction and I
lose all unsaved work and have to reconnect. The only change I am
aware of is in the modem. The software on both my home and work
computers has stayed the same.

Note that the problem exists both when I use ssh on my home pc and
home mac to connect to my work linux machine, but does not occur when
I connect to other systems, for example, browser connections remain
connected.

I'm looking for an explanation (however brief) of what's going on and
a "cookbook" solution of what I need to do to fix it.

Thanks a lot.

What are you using to ssh?  Putty or ssh-client?  If you use putty,
you can force it to send null packets to make sure you don't get
disconnected. It is in the 'connection' options  There might be an
equivalent in the ssh client on the mac.

Thanks for the comment. I am using F-Secure SSH client. What confuses
me is that with the old cable modem there were no problems, but with
the new one the system disconnects. Thanks!