ssh between computers on my home network

[Lisi <lisi.reisz@gmail.com>]

The default situation is that I can (or anyhow, could)* ssh into a PCLinuxOS 
box from the other computers on my LAN.  I can also ping the gateway, and 
could ping the PCLinuxOS computer.

The Debian computers can be neither pinged nor ssh'd to.  This is presumably 
because of some setting that Debian puts in place by default, but I can't 
find where or what.

So - what should I do, where, to allow ssh-ing between the computers on my 
LAN?  (Now all but one running various flavours of Debian.)

Thanks for any help,
Lisi

* I no longer have a PCLinuxOS box.