Library books won't open with ADE 4.0.1 on new Mac, but will open with ADE 2.0.1 on older Mac.

Using Adobe Digital Editions on 2 Macs.  Older Mac with OS 10.6 and ADE 2.0.1 opens all library books perfectly. 

New Mac with OS 10.10 (Yosemite) and ADE 4.0.1 won't open 2 library books--I click download ePub, they start to come into ADE and ADE crashes before the books load in or open.  There is no error message.  I've removed those 2 books several times from the ADE library and tried again, but always the same result.  Other books, so far, have opened OK.  The 2 that won't load or open on the new computer open just fine on the older one, so I know it's not the book files.  Any ideas on what's going on?