What is this error & how can I fix it..Unexpected Error E_10_CANNOT_OPEN

I am guessing you are using Adobe Digital Editions? Try the steps below and if that doesn't work you are best to ask on the Adobe Digital Editions Forum for product specific support.

1. Open Adobe Digital Editions.
2. Press Control-Shift-D (Windows) or Shift-Command-D (Mac OS) to deauthorize Adobe Digital Editions.
3. Choose Help > Authorize Adobe Digital Editions with you Adobe account ID(e-mail) and pass.
4. Open your document

Adobe Digital Editions

You've posted in the non-technical, non-software-specific forum Lounge.

Let us know what software you are using and a moderator can move your message to a software-specific support forum.