Rated 5 out of 5 stars
If you encounter "There was an unexpected problem when printing" - for me, deactivating the Addon, resstarting Firefox and reactivating the Addon resolved the issue.This review is for a previous version of the add-on (8.0.1-signed).
This message is always generated by Firefox when you try to Print Preview (or Print Edit) while displaying the "Add-ons Manager" tab. A slightly different message is displayed when you try to Print while displaying the "Add-ons Manager" tab. This is normal Firefox behaviour.
If you select another tab, and try to Print, Print Preview or Print Edit, you will not receive these messages.