SuSE 9.2: ssh stops working after a while

[Delfina]

Howdy

When I'm logged in to my box at home I can ssh to it remotely without
any problems. Using ssh and port forwading, I log myself out via VNC
and end the current ssh session. When I ssh in again, I can see the
Welcome login screen via VNC. All good.

However, after a while attempts to ssh to the box result in a
"Connection timed out".

Why might sshd stop listening after a while?

Any help or pointers to the relevant config would be greatly
appreciated.

Thanks

Delfina