I am a member of 4 Overdrive libraries and when I managed to lock myself out it was only from the one library. There was no effect on the other accounts at all.
My experience was extremely frustrating as I accidently returned a book I had only just borrowed. A simple (but silly!) mistake with a click in the wrong place. I have no idea why I did it!
Not only did I lose that book which had been on hold for weeks but I was locked out for nearly 48 hours and very nearly missed another hold book which became available during my punishment time.
I learnt my lesson and I am now very careful when returning my books.