The latest firmware update for my Time Capsule announced itself to me yesterday. I should have checked user forums to make sure it didn't have any ill effects, but it was all too easy just to click the 'Update Now' button. The firmware installed itself ok and rebooted the Time Capsule, only it didn't come up again. The wireless was non-existent and AirPort Utility couldn't find the Time Capsule on the wired network although it was acting as switch without any problems. The light on the front was solid amber, not flashing.
After about twenty minutes I was convinced it wasn't just being slow to come up. I attempted the generic electronic equipment solution - turn it off, then back on again. In the industry we call this 'Power Cycling'. It didn't work.
Next was the Time Capsule user guide. It says in this situation to reset to factory defaults by pressing and holding the tiny button the back of the Time Capsule with a ball point pen for five seconds. It took me a while to find the button as I use a cable lock with the locking slot. The lock obscures the reset button so you can't reset it when it is locked - nice feature! Unlocking and pressing the button for five seconds didn't have any effect. The light was still solid amber.
The next step in the user guide says to press and hold the reset button whilst power cycling the Time Capsule. I tried this and the Time Capsule came back online, but with the factory reset settings.
Luckily I had a backup of the configuration somewhere that wasn't the Time Capsule and was able to restore them without a problem. You can restore the settings from:
AirPort Utility -> File -> Import Configuration File...
To take a backup of the configuration file:
AirPort Utility -> File -> Export Configuration File...
My backups on the Time Capsule are still in tact, I would have been very upset if I had lost them, but not devastated as I have an archive of the backups on there that's about a month old, so I would have lost about a month's worth of backups.
HURRAH FOR BACKUP!