Originally Posted by JSWolf
Calibre does not support DRM. So trying to view it with Calibre's viewer will not work.
As for removing DRM, I have no idea what the issue is.
I guess I wasn't very clear. I know that Calibre doesn't support drm, but the interesting thing is that with this file, it gives the error even prior to the drm message that you would usually get, which suggests to me an issue with the epub file (?container) itself. I don't know enough about the different epub standards to know why it might work with ADE/Sony, but not other programs, or what this error truly means in terms of the structure of the file/container.