Trying to download books to my Kobo Aura HD, from public library using my MAC. After down loading content, i get a message that says "ADE quit unexpectedly. I have downloaded hundreds of books using the same kobo

Trying to borrow books from public library onto my Kobo Aura HD, using my MAC.  After downloading content, i get this message "ADE quit unexpectedly".  I have borrowed many books over the last year using the same kobo and MAC.  Can anyone help?