Occasionally (maybe 30% of the time), new videos are not imported into the database. The directory that is being scanned through iNotify is exported through NFS. (It is on the same machine on which Mediatomb is running.) I generally copy new videos from a different machine through NFS.
What I think may be happening is that as soon as the copy operation is started an iNotify event is triggered, but it is too early for Mediatomb to be able to read any metadata from the file. (There doesn't appear to be anything in the log.) If I do a "touch <filename>", a new event is triggered and Mediatomb picks it up immediately.