I successfully set up SSH key authentication on my MBL, so I edited my sshd_config to disable password authentication. After rebooting the MBL, I can't connect to SSH at all, I just get 'connection refused'. I suspect this may be because I also set UsePAM to no. Unfortunately I hadn't seen the good advice to enable Telnet as a backup.
I still have access to the web interface. Is it possible to use the firmware update function to run a script to restore my sshd_config to a working configuration? Failing that, would a Full Factory Restore restore sshd_config?
I have tried the obvious options of re-enabling SSH via the web interface and performing a Quick Factory Restore. I am running the latest firmware 02.10.09-124.
Thanks very much to anyone who is able to help, and also to everyone who has contributed so far, this wiki is very useful.