Adobe Digital Editions won't open my downloaded library books. This is the message I am getting: Error getting License. License Server Communication Problem: E_AUTH_BAD_DEVICE_KEY_OR_PKCS12

I had this problem on a Mac, using OSX and Safari, after an upgrade. I tried various suggestions, and in the end I fixed the problem by deauthorising and reauthorising ADE using instructions for a related issue ( "E_AUTH_NOT_READY") which you can find on the helpx.adobe.com site at the following link: Activation errors  This link gives instructions for Mac OS and Windows XP/Vista/7 including what to do if the standard method (CMD/Shift/D on Mac, or CTRL/Shift/D on PC) does not work.  Good luck!