E_ADEPT_DOCUMENT_OPEN_ERROR

I've bought a new e-book and everytime I try to open it with Digital Editions the download process stops just before finishing and I get this message: "E_ADEPT_DOCUMENT-OPEN_ERROR"  or "E_10_CANNOT_OPEN"  Additionally DigitalEditions crashes sometimes

I didn't change my Windows version 7 (just installed the common security updates)

I already tried these options: uninstall-reinstall, update DigitalEditions to 4.59, try to run it with the Windows compatibility assistant. Nothing works out.

I've already searched for solutions in community-forums but without success. (There are more people with the same problem, but they had changed to Windows 10 before. I didn't do this.)

The e-book I had bought and downloaded before still work.

If anybody has an idea how to solve this bug, many people (including me) would be very happy.