Opening downloaded books

Regular  buyer of Ebooks from Ebooks.com. Downloaded with success until I changed to Windows 8.  Just bought some books, tried todownload to my computer in order to pass them on to my Sony Reader.  But .... message received says

"Adobe Reader cannot openURL Link (2) acsm, as the type of file is not taken in charge OR the file is damaged (it was sent as an attachment and was not decoded correctly, for example)"  This has not happened before I changed to Windows 8, and I would really love to download the books I've just purchqsed. Thaks for any help! (I'm not conversant with the language of computers!!)