When Firefox extensions don't load / show properly

After updating to Firefox 19, I noticed that some of my extensions did not load or show properly, such as No Script.

To fix this I needed to delete some stuff, and allow Firefox to recreate:

1. Open your profile folder:
   
   Click Help > Troubleshooting Information.
   
   Look for the section "Profile Directory" and then click "Open Directory". This open the folder where your profile is stored.
   
2. Quit from Firefox
   
3. In the profile folder delete these files:
   
   extensions.sqlite
   extensions.ini
   
4. Restart Firefox. You might be asked if you want to enable some extensions, so choose what you want to do and then restart if required