Originally Posted by Catlady
But the e-reader needs to be authorized with the credit card number, and it has to match what's on the BN account.
I got my e-reader (which read BN's DRM) two years ago, and at the same time had changed my credit card on the BN account, and entered that into the e-reader. I had a bunch of books I'd downloaded with the Nook for PC program, with an earlier credit card. I could not read any of them on my e-reader; I had to redownload everything.
Sounds like your ereader only saves one encryption key, and wants all books to be encrypted with that key. Bad DRM support in your ereader's software.
When you try to open an ebook for which the ereader has no encryption key, it should ask you to type in the correct credit card number and name.