Thunderbird recently decided to forget all about my profiles and configuration after the computer’s power had suddenly been cut off while thunderbird was closing. The problem was that thunderbird was stopped in the middle of writing the prefs.js file located within the profile’s directory, hence some sanity check failed when the preferences were reloaded and they were erased.

Luckely it wasn’t harder to restore than to fetch a recent backup and replace the prefs.js file. I would however have been able to save myself that trouble if I had stayed calm the first time thunderbird launched with a blank screen (instead of immediately restarting thunderbird) by copying the prefs.backup file stored in the profile directory. The prefs.backup file is thunderbird’s a backup of the prefs.js file which contains the state of the file prior the most recent change (i.e. it contains the working configuration the first time thunderbird launches with a corrupted configuration).