Todoist plugin partially incompatible with "Classic Theme Restorer", Firefox ver 29
If the plugin "Classic Theme Restorer" is installed and enabled before installing the Todoist plugin, on restarting Firefox, the ui will be so badly damaged (no urlbar, no search bar, no config button, etc - although the Todist icon is present!) that about the only resolution is either to restore from backup, or to build a new profile.
Solution - disable or remove "Classic Theme Restorer" before installing Todoist, restart, then re-enable.
This can easily be repeated in a test profile. Simply build a new profile, install "Classic Theme Restore", restart, install Todist, restart and ... BANG. Or rather, whimper.