Hi olandese, welcome to MobileRead.
That is a new behaviour and to be honest I can't think how it could be related to the plugin.
- What do you mean "not able" to open the book - exactly what happens?
- What action are you doing to open the book?
- If you run Calibre in debug mode using ctrl+shift+r can you post any messages that appear when you try to open a book in this scenario.
- What book format(s) does this apply to that you are scanning/opening.
- Does this apply to all books or just specific ones?