I have been using adobe digital editions sucessfully til 3 days ago but now i get an error message

I down load a book from my library and when the down load appears on the botton of the screen and I clikc on ot to down load it to digital edditions an error screen appears on the digital editions screen in staed of the book which says transmission error verrify that the computer is connected to the internet. The computer id clearly connectedto the internet as I have already been on the library web site. I tried uninstalling the digital editions software and reinstaliing it but that did not help. any suggestions how to fix this?