Can't transfer from Adobe Digital Editions to my Nook

E_IO_WRITE - Failed to write to destination file

This is the error message that I get. I has cost me money and this is the third time it has happened. I am buying books from e-books.com. They have done everything they can and it still isn't fixed. Please help me. I am almost 80 years old, very sick and confined to my bed. I really need my books.

Thank you in advance,

Lenora Underwood