ssh: No route to host

[John Wilkes <john.wilkes@gmx.de>]

Hello List,

I've recently transferred my computer and my mother's over to Debian.
They were both running SuSE before. I used to ssh to my mother's
computer to perform maintenance, but that doesn't work now.

When I try to ssh to her computer, I get the error message:

ssh: connect to host XXX.XXX.XXX.XXX port 22: No route to host

My mother's computer is hiding behind a router which acts as a firewall,
but port 22 is open - it worked with SuSE and I haven't changed the
settings. There is no software firewall, at least none that I'm aware
of.

My computer has Lokkit installed; I've told this to expect ssh, but no
joy. I've also switched it off altogether with no change. (this is only
for incoming ssh, though...?)

I can ping my mother's computer, so it's not the network that's at
fault. The sshd_config file is the one installed by default.

Both computers are running Sarge with a 2.6.8 kernel.

I'd be very grateful for any ideas on this.