Server stopping after left idle?

[xoft]

That message means that something is already listening on the port, or there was some other obscure error. Do you have another Minecraft server running on that machine? If you change the port number in settings.ini (with the server not running, of course), does the message appear after starting the server? If you do a "netstat -nlat" while Cuberite is not running, do you see the port 25565 as used?