I'm having a similar problem but with a library book and Adobe Digital Ed - I copied the book to my Kobo before the firmware upgrade but only tried opening it after the firmware upgrade and now it's telling me it's locked - so I suspect the firmware upgrade botched something.
I've tried deleting the offending book from the kobo and putting it back on but it gives me the same error when I try to open it on my kobo: "the content you are trying to view is locked. please use your adobe id to authorize your ereader with ADE"
except my ADE is authorized and I have previously successfully put books on my kobo with it. And the library book is still good - I can read it on my computer.