Where was the book obtained from? How did you download it to your computer? ADE 2? ADE 4? calibre's DeACSM plugin?
I suspect the key lines are:
Code:
calibre_plugins.dedrm.DeDRMError: DeDRM v7.2.1: Couldn't decrypt after 0.5 seconds. DRM free perhaps?
DeDRM v7.2.1: Trying to decrypt hfrx0vau.epub
DeDRM v7.2.1: Verifying zip archive integrity
DeDRM v7.2.1: “hfrx0vau.epub” is neither an Adobe Adept nor a Barnes & Noble encrypted ePub
If the epub is indeed DRM free, I would suggest opening it in calibre's editor and running, preferably, epubcheck (you will need to install the plugin) or the builtin error checker.
If the epub is not DRM free, it may encrypted with Adobe's hardened DRM.
Just to check, you might want to install NoDRM's updated version of the DeDRM plugin. See the
New version of DRM removal tools ("DeDRM") thread in the News forum. The download link should be in the first message in the thread.