I originally saw this problem with MC 17 (see
http://yabb.jriver.com/interact/index.php?topic=73469.0).
Last night I installed MC 18.0.51 and imported all my ripped DVDs into a new library . Now I'm seeing a number of movies with the Duration field missing. Some are also missing their Dimensions and Bitrate information as well. Some, worked fine in MC 17, but are missing Duration and Dimensions in MC 18. Others are missing the information in both versions. In one case, however, the import actually fixed an issue with the Duration being far too short. I found that I could also fix this problem in the MC 17 library by updating the library from tags; however, this operation does not fix movies with no Duration information.
My primary method of playback is via a PS3 over DLNA. Without the Duration attribute, the movie refuses to play over DLNA. The PS3 returns the message:
The folder could not be accessed. This content may have been deleted from the media server.