I get this message when trying to open a particular DNG file. Same error when I try to open the backup versions on archive drives. All other files in the same job open as expected without problem.
BTW, iView is able to extract the full-size jpeg from the DNG, so the problem seems to be something with the RAW file itself...
What causes this error? Systemic problem, or incidental glitch?
Is there any way to recover the file?
How to prevent such errors in the future?
It could be just a corrupted file. It's hard to know what the problem is in that situation. Do you still have the original raw files? You could try converting it again.