Ciao ho avuto lo stesso problema anch'io stamattina...quando ho registrato il mio ID su Adobe ci dev'essere stato qualche problema di connessione al server. Ho anche io due ebooks che non riesco ad aprire...non so proprio come fare.
I had no luck in getting advise from Adobe. I could not find any proper instructions on any forum. But i did manage to solve the problem. I might as well share my experience for those who are interested. Important to mention: i had only 2 ebooks with the same error message: "E_ADAPT_INTERNAL". I had no other ebooks on my computer. Another thing to mention is: you can only download the ebook several times (3 times??). This is a trial and error solution that worked for me. It might, might not, work for you.
(Working on MacBook Pro -Retina, OS X Yosemite 10.10.2, Digital Editions 4.0)
01. trash the downloaded ebook file (in my case: AdobeAfterEffectsCCClassroomi.acsm)
02. empty trash
03. trash the "activation.dat" file. (library -> application support -> Adobe -> Digital Editions)
04. empty trash.
05. uninstall Adobe Digital Editions by moving it to the trash.
06. empty trash.
07. restart computer
08. clean all cashes (did a deep cleaning with Yosemite Cash Cleaner - Northern Softworks)
09. restart computer
10. install Adobe digital Editions 4.0
11. download the ebook again
12. open the ebook in Adobe Digital Editions
Hope some of you find luck in this workflow.